Bottle-Life Calculator

Cost per use + when you'll run out.

Price ($)

Size (ml)

Amount per use (ml)

Uses per day

PAO — period after opening, in months (optional)

Quick presets

The numbers

Cost per use: $0.833
Monthly spend: $50.00
Total uses: ~60
Runs out: Jul 26, 2026

What this does

A $90 serum that lasts 9 months costs $0.33 a use. A $20 serum that lasts 3 weeks costs $0.95 a use. The Bottle-Life Calculator strips the sticker shock out of skincare math: enter price, size in ml, and how much you use per application. Get exact cost per use, projected monthly spend, and the date the bottle will run out.

Plan your re-orders. Stop double-buying. Realize that the cheaper bottle is actually more expensive. Or, occasionally, realize that the luxury product you have been avoiding is actually within your budget.

What you'll get

Cost per single use, rounded to the cent
Projected monthly spend on this product
Run-out date — schedule your re-order
Comparison to a second product, side by side

FAQ

How do I know how much I use per application?

For most serums, two pumps is roughly 0.5 ml. Moisturizers vary — a pea-size is roughly 0.3 ml. The tool has presets.

Does it factor in product expiry (PAO)?

It will note PAO if you enter it, so a bottle that "should" last 18 months but expires at 12 months gets the right run-out warning.

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