How the moisturizer run-out date is worked out
In dry-skin and eczema care, the thing that usually slips is not which product you pick but how much of it you use. Applying enough empties a tube faster than people expect, and an empty tube turns into a skipped day. This calculator takes the product size in oz or fl oz, the amount per application in the same unit and the applications per day, then reports the days until empty, the date it runs out, and the monthly amount and tubes on a 30-day basis.
The arithmetic is multiplication and division only. The daily amount is the amount per application times the applications per day, and the days until empty are the product size divided by that. Tubes per month are the monthly amount divided by the product size, rounded up once at the end, and the run-out date adds the rounded-up days to the start date. Zero, negative values, and an application larger than the whole product all bring up a message instead.
For reference, one fingertip unit is about 0.5 g (0.02 oz) and covers two adult palms (Long & Finlay 1991). It was defined for prescription creams and moisturizers are usually used more generously, so enter the amount you actually use per application. No severity score for your skin is produced either. Current as of October 2026, and not a medical diagnosis. Weeping, pus, or redness spreading with warmth should be seen by a clinician.
Frequently Asked Questions
One fingertip unit (FTU), a line squeezed from the tip of an adult index finger to the first crease, is about 0.5 g (about 0.02 oz) and covers an area of two adult palms (Long & Finlay 1991). That unit was defined for prescription creams, and moisturizers are usually applied more generously, so weigh a few applications on a kitchen scale in ounces (or grams divided by 28.35) and enter the average; the days until empty then track reality.
Choose fl oz, enter the size as printed and measure each application in fl oz too. Fluid ounces measure volume and ounces measure weight, so they are not one to one; mixing them makes the days until empty drift a little. For thin lotions the gap is small; for thick creams it grows.
Because you cannot buy half a tube. Needing 1.2 means keeping 2 on hand to avoid a gap. The rounding is applied once in the final step, not at each intermediate stage.