Daily or monthly: which costs less

Daily lenses always look like the expensive option: a box of 90 costs more than a box of monthlies that lasts for months. But the right comparison is not between boxes, it is between what you spend in a year the way you actually wear them. Dailies are paid only on the days you use them; monthlies are replaced every month even if you wore them twice, and they need solution and a case.

This calculator compares the annual cost of the two options, shows how much you save with the cheaper one and finds the number of days a week at which they break even. It works in any currency.

How the calculation works

Enter how many days a week you wear lenses, the cost of a pair of dailies, the cost of a pair of monthlies for one month and how much you spend each month on solution and cases.

• Dailies: cost per pair × days of wear per week × 52.
• Monthlies: (cost per pair + solution) × 12, whatever the use.
• Break-even: annual cost of monthlies divided by the annual cost of one pair of dailies worn one day a week.
• Monthlies per day of wear: annual cost of monthlies divided by the days you actually wear them.

The verdict is based on the ratio between the two annual costs, which does not depend on the currency.

How to work out the cost per pair

For dailies, divide the box price by the number of lenses and multiply by two: 90 lenses at 49.50 make 0.55 per lens, that is 1.10 per pair. For monthlies, a box of 6 lenses holds three pairs, so three months: at 27 that makes 9 per pair per month. If you have two different prescriptions and buy two boxes, add the prices and divide by the total number of pairs.

How much the days of wear matter

The table uses the example above: dailies at 1.10 per pair, monthlies at 9 a month plus 6 of solution, that is 180 a year for monthlies.

In this example break-even falls just above 3 days a week. People who wear lenses only at weekends, for sport or for evenings out spend less with dailies; people who wear them every day save over 200 a year with monthlies.

What each day really costs with monthlies

The cost of monthlies is fixed, so the cost per day of wear falls the more you wear them. At 180 a year:

Just compare this column with the price of a pair of dailies: when the per-day cost of monthlies is higher than that of dailies, dailies win.

Break-even depends on the price of dailies

With monthlies at 180 a year, here is where break-even falls as the cost per pair of dailies changes:

Large boxes of dailies lower the cost per pair and move break-even towards daily wear: it is worth comparing the 30-pack with the 90-pack.

The four bands of the verdict

• Dailies below 80% of monthlies: dailies clearly win.
• 80% to 100%: dailies cost a little less; comfort and habits matter as much as price.
• 100% to 125%: monthlies cost a little less, but the convenience of dailies may be worth the difference.
• Above 125%: monthlies clearly win.

Beyond price

Dailies need no cleaning or solution and are thrown away at the end of the day, a convenience valued by people who travel or wear lenses irregularly. Monthlies need a cleaning routine and a regularly replaced case, but produce less packaging to dispose of. The right type of lens for your eyes should be chosen with your optician or eye doctor: not every prescription is available in both formats.

Limits of the calculator

The model assumes monthlies are replaced every month as the manufacturer indicates, even if little used, and that dailies are used only once. It does not include eye tests, backup glasses, shipping or subscription discounts: if you have them, include them in the cost per pair or in the monthly item.

Frequently asked questions

Are daily or monthly lenses more expensive?

It depends on how many days you wear them. With dailies at 1.10 per pair and monthlies at 180 a year including solution, dailies cost less up to about 3 days a week, monthlies beyond that.

How do I work out the cost per pair of dailies?

Divide the box price by the number of lenses and multiply by two. For example, 90 lenses at 49.50 make 1.10 per pair.

How do I work out the cost per pair of monthlies?

A box of 6 monthly lenses holds three pairs, that is three months: divide the price by three. At 27 a box that makes 9 per pair per month.

Can I use monthlies longer if I wear them rarely?

No: monthlies should be replaced on the schedule the manufacturer gives from when you open them, even if you wore them only a few times. That is why their cost does not fall with lighter use.

Can I reuse daily lenses?

No, they are designed for single use and should be thrown away at the end of the day. The calculator assumes a new pair for every day of wear.

How much does solution for monthly lenses cost?

It depends on the product and size, but it is usually a monthly cost worth counting. Enter it, together with replacing the case, in the dedicated field.

What does break-even in days per week mean?

It is the number of days of wear at which the two options cost the same. Below it dailies win, above it monthlies.

Is it worth buying large boxes of dailies?

Usually yes: the 90-pack costs less per lens than the 30-pack and moves break-even towards more frequent wear.

What about two-weekly lenses?

To use them with the calculator, enter the cost of two pairs, that is one month's spend, in the monthly field.

Does the calculator include eye tests and glasses?

No, it only compares lenses and solution. If you like, add other recurring costs to the monthly item.

Are daily lenses more hygienic?

They need no cleaning or case, so they remove maintenance mistakes. The right type of lens should still be chosen with your optician or eye doctor.

Does it work in any currency?

Yes. Enter all prices in the same currency; the verdict is based on the ratio between costs, which does not depend on the currency.