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Contact Lens Prescription VS Glasses Prescription

When you set out to order contact lenses online, you have to come prepared with a certain amount of information. The most important piece of information is your contact lens prescription. You may have mentally checked this item off in your head when you received your glasses prescription from your optometrists, but this might lead you into error.


I am not a doctor. The information on this page is for educational purposes only, and it is not to be taken as medical advice. 

Please read Contacts Advice Terms of Use before continuing.

Contact Lens Prescription VS Glasses Prescription

Calculating a Contact Lens PrescriptionYour glasses prescription is different than your prescription for contact lenses, and unless you paid your optometrists a special fee to specifically obtain your contact lens prescription, chances are you don’t have the correct numbers for your contacts.

Certain prescription for glasses must be converted using a special equation, followed by some rounding based on the limited range of available powers in contact lenses to arrive at the numbers you can use to order contact lenses online.

If you attempt to order contact lenses using the exact numbers written on your glasses prescription, you will often run into the problem where the numbers on your prescription are not available for the brand of contacts that you’re trying to order. That is because contact lenses don’t come in nearly as many power options as glasses do. That’s why the conversion is essential.

Even if all of the numbers on your glasses prescription do happen to be available for the brand you’re shopping, ordering your contact lenses in the exact same numbers as what’s written on your glasses prescription can lead to eyestrain and blurriness while wearing your contacts.

Why Won’t Your Doctor Give You A Prescription For Contact Lenses?

If your optometrist knows that you wear contact lenses, why doesn’t he/she just automatically give you a prescription for contact lenses as well as for glasses?

There are many reasons why they don’t.Measuring Glasses Prescription

Contact Lens Fitting Fee

The main reason is because it’s an opportunity for them to generate more income. Your optometrist is perfectly capable or converting your glasses prescription to contact lenses, and can do so in just a few seconds. However, since the ability to perform these conversion requires unique knowledge, they feel justified in charging an extra fee for it. This contact lens fee can run anywhere from $40 to upwards of $70.

The Fit Must Be Assessed

But there’s a little more to it than that. They are also constricted by their profession’s regulatory bodies. Since contact lenses are considered medical devices which can have some negative side effects on the health of your eyes if they are not fitted or worn properly, optometrists are not suppose to prescribe you contact lenses unless they have first ascertained the safety of said contact lenses on your eyes. This is also part of why they charge you an extra fee, because it takes them more time.

Retain Sales

On top of the contact lens fee, your optometrist wants to your purchase your contact lenses from his/her office. Giving out contact lens prescriptions to every single person makes it all too easy for them to take the numbers and go buy somewhere else that’s less expensive. As a result, most eye doctor offices will only work out your contact lens numbers if you’ve committed to purchasing your contact lenses from them.

Getting your prescription from your eye doctor and purchasing your eyeglasses and contact lenses elsewhere is viewed as being disloyal to them, so to discourage that behavior they try to resist handing out prescriptions as much as possible. In many, if not all places, optometrists are legally required to hand out prescriptions for glasses to anyone who has one. But no such regulation exists for contact lens prescriptions, so they tend to keep them in-house.

Where Else Can You Get A Contact Lens Prescription?Local Chain Optical Store

So if optometrists won’t give you a contact lens prescription unless you buy contact lenses from them, and you want to purchase your contact lenses somewhere else, what do you do?

Well as we all know there are many other places you can buy contact lenses from other that your eye doctor’s. In every big city there are independent and chain optical stores on almost every street corner. Most of these places also sell contact lenses.

If you take your glasses prescription to one of these places, they most likely (though it’s not a guarantee), they will have someone working there who is trained in converting prescriptions from glasses to contact lenses.

However, similar to your eye doctor’s office, they have absolutely to incentive to convert your prescription for glasses to contact lenses if you have no intention of buying contact lenses from them. Doing so would be a waste of their time and it would most likely be helping out one of their competitors.

So, if no matter where you go you can only get your glasses prescription converted into contact lenses by the people at the store where you end up buying your contact lenses, what happens if you want to buy your contact lenses online?

What If You Buy Contact Lenses Online?

Ordering Contact Lenses OnlineOnline contact lens retailers are the natural enemy to your local optometrists, local optical store, big box optical store, etc. The internet easily out-competes (on price) any physical store that sells contact lenses because the cost of operating a website is drastically lower that the cost of operating a brick-and-mortar store. Therefore, the cost savings are passed on to the consumer.

Nowadays, websites that sell contact lenses are a dime a dozen. This would not be the case if tons of people weren’t buying their contact lenses from them. But where are all of these people getting their contact lens prescriptions from?

The unfortunate reality is that many people are simply using their glasses prescription to order contact lenses online, and just filling in the gaps on their own if there are numbers on the glasses prescription that aren’t available in contact lenses. This is not conducive to a healthy and enjoyable experience in contact lenses, as for many people this will result in them ordering the wrong power.

Remember, not every single prescription for glasses needs a conversion. For people with very low and simple prescriptions, the power in the glasses and the contact lenses are actually the same. But for anyone with a significant amount of nearsightedness, farsightedness or astigmatism, there is a difference.

What’s The Solution?

That’s a great question. Currently, your only real option to make sure you’re ordering the correct contact lenses is to discuss it with your optometrist. If you explain that you intend to purchase your contact lenses online, and that you would like all the information required in order to do so, your optometrist may or may not give you the information. And unless your optometrist is very generous with his/her time, expect to have to pay a fee for this service.

If you’ve ordered your contact lenses online in the past, please share how to you go about getting the numbers you use to order your lenses in the comments below.



Author Julie

More posts by Julie

Join the discussion 34 Comments

  • Alyssa says:

    Hi Julie,
    I’ve been wearing glasses for about 6 years now and I’m considering switching to contact lenses. What are the benefits of contact lenses over glasses? I think your article mentioned that there could be some negative health problems due to contact lenses? What should I be concerned about, if anything? What advice to you have for someone thinking about making the switch to contact lenses?

    • Julie says:

      I wouldn’t recommend you ‘switch’ fully from glasses to contact lenses, but rather ‘switch’ to from wearing only glasses, to splitting the time between contact lenses and glasses. It’s not healthy for your eyes to wear only contact lenses, all day, every day. My main advice is don’t over-do it with the contact lenses. Your eyes need breaks from contacts at least 1 or 2 days per week ideally.

      If you don’t over wear your contacts (not more than 10-12 hours/day, 5-6 days/week), and you practice good hygiene with them, you will be successful 🙂

      Since you’re new to contact lenses, I would recommend you start by checking out my contact lens brand selection guide. http://contactsadvice.com/contact-lens-brand-selection-guide-find-the-perfect-contact-lens-brand-for-you

  • Erin says:

    Wow, I never knew about all the regulations surrounding a prescription for contact lenses!! I have only wore contact lenses for a short period of time, many years ago, so only require a prescription for glasses. I have obtained a copy of my prescription and taken it elsewhere to purchase glasses and felt a bit dishonest for doing so. That is funny when you think about it, after all, it is my prescription. While every eye professional is in business to make money, this feels deceptive. You provide an exceptional value in converting a prescription for glasses to one for contacts. When I read you instructions on how to do it for myself, it becomes a no-brainer to give you $5 to do if for me

    • Julie says:

      Hi Erin! Thanks for your feedback! I tried to make the instruction on how to convert a prescription from glasses to contact lenses as clear and simple as possible, but frankly, it’s rather difficult to explain over the internet.

  • Josh says:

    Hi Julie,
    I have been wearing glasses for almost 10 years now and not once has anyone ever told me that the prescription for glasses is not the same as that of contact lenses. This is the first time I’ve ever read about this. Even online sites from where you can order lenses in bulk [and save money] never talk about this.

    Thanks for the great informative post.

    • Julie says:

      Hi Josh, yes I have noticed that too. And I have wondered what numbers people have been using to order their contact lenses online all these years… If they have just been using their numbers for glasses, then I’m afraid a lot of people have been ordering the wrong numbers for their contact lenses.

  • stefan says:

    I have used contact lenses for a long time and now I have returned to glasses. I think it is really important for people to get their right prescription but the problem is the lack of information and also the high price charged for it.

    It is really nice to have people like you who can offer this service and lower the costs of using contacts.you are also doing a great job warning people about the importance of getting the right prescription.



    • Julie says:

      Hi Stefan! I agree, the price that some places charge for a ‘contact lens assessment’ is unreasonable. They will spend just a few seconds to convert your glasses prescription to contact lenses, and charge you $70 for it. If for that $70 you get to take home trial lenses of several different brands and test them out, and have the optometrist professionally assess the fit of each one, then at least you are paying for something worthwhile. But I kid you not, many places, particularly big box store chain opticals, will charge you $70 just to do a conversion on the numbers in your prescription that you can do yourself.

  • Carroll says:

    Hi there Julie, I was going over your website for curiosity sake. My cousin is a optometrist. I never knew that the prescription would be different for contact. I did not start wearing glasses until my 50’s. Now I would wear contacts. In any case you have a Great Day and thanks again.

  • Nate says:

    I recently started wearing glasses due to my vision getting worse the more I stare at my computer and phone screen but the glasses can be very uncomfortable if I’m wearing them for long periods of time. It’s good to know that my glasses prescription might not be the same as my contact prescription. Do you recommend disposable contacts or something else?

    • Julie says:

      If you’re new to contact lenses I would suggest you go with daily disposables. They are comfortable and hygienic compared to contacts that you re-wear day after day. Before you start shopping for contacts, make sure you check out my top recommended brands!

  • RuthM says:

    I had no idea it was so complicated. I wear glasses for the computer so I am not in the word of contact lenses, yet, but I would naturally have thought, like so many, that the prescription is exactly the same.

    It’s a bit cheeky to charge all that extra to convert a few numbers. I will share your fiver contact with a couple of friends of mine who wears contacts, perhaps it can help them. Thanks!

  • FortheLoveofDOG says:

    As an avid contact wearer I have often struggled in getting new contacts because as you state many offices won’t give the prescription, I actually had one office that offered as long as I paid an additional fee for it, which I refused since I paid for the service of having my exam done there. I’ve since found an office that automatically provides it after the eye and fitting exams, which is great. I think your Fiverr Gig is really a really important offer, especially when it comes to the eyes, getting a good conversion and help to ensure everything is correct when ordering online is great.

    • Julie says:

      Hi! That’s great that you found a place that will give you the numbers that you need without charging you for it! I think it would be nice if all places did that. It might hurt their bottom lines, but it would be much better for the consumers.

  • TerryB says:

    What a great post!

    I have been wearing contact lenses and glasses for 20 years now and never knew that contact lenses have different prescriptions than glasses.

    I had a few optometrists and none have told me this. When I ask for my prescription, I always receive one (not one for each).

    I know I have to get my eyes checked as my contact lenses are becoming a bit blurry. I always wanted to know how long is to long to wear contacts during the day?

    ps. and yes, I buy my contacts online – much cheaper!

    • Julie says:

      Hi Terry! Unfortunately for people who prefer to buy their contact lenses online, most optometrists are unwilling to help them out by giving them the correct contact lens numbers. I would be happy to review your prescription before you purchase your next contact lenses to make sure you get the right numbers.

      As for how long you should wear your contact lenses, check out this article I wrote on the topic: http://contactsadvice.com/how-long-can-you-wear-your-contact-lenses-for

  • Theresa says:

    I have worn glasses since I was 8 years old. I know very long time! I have begun wearing contacts when I was about 16, just recently a pair of my glasses broke and I know that I have to make an appointment at the eye doctor soon. It’s funny that I came across this post because I wasn’t sure if I was going to get a glasses eye exam, contacts, or both, according to your post I should do both so that I know that I will get both prescriptions just in case I decide to go somewhere else to get my contacts

    • Julie says:

      Yes that’s right. If you don’t request (and pay for) a contact lens exam, your optometrist will likely not give you the numbers you need to use in order to purchase your contacts online. If you simply go to a different store, most likely there will be someone there to help you convert your numbers, but online, I don’t know any other site except this one that can help with you with the conversion.

  • lifebeginswithyourhealth says:

    You have provided a great article on contact lenses without a doubt, I only need glasses for reading so I was wondering if contact lenses is a option for someone who only needs vision assistance for reading? Also I have extremely dry eyes, I use prescription eye drops so would contact lenses be a problem for someone with my problem?

  • jazzy323 says:

    This article interested me a lot because i used to wear contact lenses but i dont anymore due to the price and the fact that they were not prescription….are prescription contacts more expensive? i think its wrong that optometrists wont give a prescription unless you buy contacts from them as it sounds like they dont care

    • Julie says:

      Yes you’re right, it does give off that impression. I think that most optometrists would love to help you out, but they also want to be compensated for their work if they do. There’s so much competition out there for them now from independent opticals, big box chain opticals, and the internet, that they feel that have to push back in this way. It is what it is I guess…

  • Scott says:

    I wish I had read this information before. I have problems with my near vision as I got older and decided to try a multi-focal contact to help me see. I got tired of taking glasses off and on all the time. I didn’t understand that these were 2 separate examinations so when I decided the contacts were too much trouble for me, I had to pay for a whole different exam to get my glasses changed. What a pain!

    • Julie says:

      Hi Scott, you’re right, it can be quite a process. If you don’t mind me asking, what was it about wearing contact lenses that you thought was too much trouble?

  • Chris says:

    Wow, I wasn’t aware there were separate prescriptions for glasses and contacts. I understand optometrists are running a business and don’t want to lose clients. Charging upwards of $70 is a bit much though.

    It’s awesome that you’re charging $5 for the conversion. It seems a lot more reasonable.

    My daughter wanted to order some non-prescription contacts for her cosplay. They looked nifty, but her mother said no because she didn’t think they were safe. If I recall correctly, they were sold online and coming from China. What are your thoughts? Do you think these types of contacts are safe enough to wear, or it is a good idea to avoid them altogether?

    • Julie says:

      The are definitely not the safest contact lenses out there. Personally, I would rather stick to brands of contact lenses that have been approved for wear by the FDA or Health Canada (or whatever health regulatory body exists in your country). Costume and cosplay lenses come from who knows where, and who know what they’re made from, and under what factory conditions, etc.

  • Cherilyn says:

    Hello, I don’t actually wear glasses or contact lenses as I don’t really need them but I am very in to special effects make up and I would like to use contacts for certain makeup looks.

    Would you recommend against this? and if I do so, instead of buying the ones that could be found online I would be better speaking to a doctor first as I know the cheap ones online can actually damage eyes, am I correct?

    • Julie says:

      There are some color contact brands that are reputable and safe. These are the brands that have been tested and approved by health regulatory bodies like the FDA and Health Canada. My favorite of these brands is called Air Optix Colors. However, there are hundreds of places where you can get all sorts of different colored/costume/theater lenses that are not FDA/Health Canada approved, and I would stay away from those.

  • Ben says:

    Wow, I never knew that there is a different precription for lenses and for galsses. I though it was one and the same. I wear both glasses and lenses, and since I recently took to buying most of my things online, I am contemplating buying lenses online too. not being able to convert glasses to lenses would complicate things. I will be needing your help when it’s time to order lenses. Thanks for offering this service!

    • Julie says:

      Hi Ben! Hasn’t online shopping made things so much easier for us? I’m glad you found my site. I look forward to helping you with your prescription 🙂

  • Jackie says:

    Great informative post. I actually think i did this years ago. (when contacts initially became available online). It always bugged me that my eye doc tried to wring more money out of me as well. When I figured it out and tried to get the prescription, they wanted to charge me for another appointment. Thanks for the educational post. I think many will benefit from it.

    • Julie says:

      There’s a lot of ways in which your optometrist can and can’t charge you.

      For example, if you pay for an eye exam, that typically doesn’t include your contact lens prescription. They can’t charge your for your contact lens prescription itself, but they can charge you for the visit that is required for them to determine your contact lens prescription.

      I know in some places, it gets a little sketchy, and you get charged for a contact lens assessment, but they don’t really assess you, they just assume all the details and simply write you a prescription. In that case it may seem like you just paid extra to get a contact lens prescription, but that’s only because the doctor skipped a few steps…

      No two eye doctors are the same. Some like to follow the rules, and others like to bend them. That’s why it’s important to be careful and stay informed out there.

  • Marlaine says:

    I was really hoping to be able to get contact lenses now after wearing glasses for about 10 years. But at my latest appointment the optometrist said the likelihood of me being happy with contacts was about 10% — I am near-sighted in one eye, far sighted in the other. Both are minimal – I wear glasses to stop me from getting headaches. I can see fine without them. I’m tired of glasses though. Do you think maybe I should just push forward to try them out? Request the prescription regardless and order some to try out?

    • Julie says:

      Hi Marlaine, what an interesting story! Has your doctor explained to you why he/she thinks that you’d be a poor candidate for contact lenses? From the information that you’ve presented, I don’t see why you wouldn’t be a great candidate.

      In fact, contact lenses are often recommended for people who have large differences in prescriptions between the two eyes. Why? Because when the prescriptions are very different, especially if one eye is nearsighted and the other is farsighted, glasses create a difference in magnification/minification between the two eyes. This can be very uncomfortable for some. Contact lenses don’t create this problem at all (is has to do with how close they are to your eyes).

      And finally, the people who tend to succeed with contact lenses the most, are the people who are the most motivated to succeed. You definitely seem to be motivated to try contact lenses. If your doctor allows, and you trial contacts under his/her supervision, I think you’ve got nothing to lose!

      Hope that helps 🙂


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