Lash fill or new set?

Worked example

35% of your extensions left, your salon wants at least 40%, set $200, fill $75, worn 3 weeks. 35 is below 40, by 5 points, so the likely booking is a new set at $200. A fill would have been $75, a difference of $125, which is $25.00 against $66.67 per week of wear (75 / 3 and 200 / 3).

How it works

Recommendation = fill if percent remaining is at or above the minimum, otherwise new set. Cost per week of wear = price / weeks you expect to wear that appointment.

What this is not. There is no published industry standard for how many extensions must remain; the default of 40 percent is a common rule of thumb, and many salons also look at how the remaining lashes sit, how long since the last fill and what an artist can fill in the time. The percent left is your own estimate. The tool only shows what the arithmetic says given your salon's number.

Sources and basis (opened 2026-10-08): arithmetic on the numbers you enter; no external rate is applied. The minimum-remaining figure is a common rule of thumb, not a published standard, and is yours to set.

FAQ

How many lash extensions need to be left for a fill?

There is no published standard. A common rule of thumb is that somewhere around 40 to 50 percent should still be on, and each salon sets its own cut-off, so ask yours when you book.

Why would a salon book a full set instead of a fill?

When too few extensions remain, a fill takes nearly as long as a new set. Salons usually price the appointment by the work involved, so they move you to the set price.

Is a fill always cheaper?

Per appointment it is, since the fill price is lower than the set price. The tool also shows cost per week of wear so you can compare both for the time you plan to wear it.

How do I estimate the percent left?

Look at each eye in a mirror. If roughly half of the extensions have shed, enter 50. If most of the original set is gone and only a scattering remains, enter a low number like 20.

Does waiting longer save money?

Waiting between fills lowers the number of appointments in a year, but if the share left drops below your salon's minimum you can end up paying the set price instead of the fill price.