Cost per use: the math behind “buy it for life”

A price tag on its own doesn't say whether a purchase is worth it — a $180 coat and an $18 coat aren't really being compared on the same terms unless you also know how many times each one gets worn. Cost per use puts them on the same footing: price ÷ expected uses.

The formula

Cost per use = price ÷ number of times you expect to use it. A high cost per use is the signature of an impulse buy that mostly sits in a closet; a low one — even on an expensive item — is often money well spent, because the price gets spread over so much use.

A real example: two winter coats

One coat costs $180 and gets worn twice a week across a 20-week winter. A cheaper $45 coat looks tempting, but it's worn just as often.

1. Expected uses: 2 × 20 weeks = 40 wears, for both coats.
2. $180 coat: $180 ÷ 40 = $4.50 per wear.
3. $45 coat: $45 ÷ 40 = $1.13 per wear (rounded).

At equal use, the cheaper coat is cheaper per wear too — cost per use doesn't automatically favor the pricier item. It only changes the answer when the pricier item is also used more, or lasts longer, which is exactly the next example.

A real example: cheap shoes vs. shoes that last

A $25 pair of running shoes wears out after about 40 runs. A $110 pair, built to be resoled and repaired, lasts 300 runs before it's actually done.

1. $25 shoes: $25 ÷ 40 = $0.625 per run, i.e. about 63 cents.
2. $110 shoes: $110 ÷ 300 ≈ $0.367 per run, i.e. about 37 cents.

The $110 pair costs more than four times as much up front, but ends up cheaper per run by about 26 cents — because it lasts nearly eight times as long. The sticker price and the real cost pointed in opposite directions.

A real example: a gadget that mostly sits in a drawer

A $45 kitchen gadget gets used once a month.

1. Uses in the first year: 12. Cost per use: $45 ÷ 12 = $3.75.
2. If it's kept and used the same way for 3 years: 36 uses. Cost per use: $45 ÷ 36 = $1.25.

Cost per use falls every extra year the thing keeps getting used — which is also the honest warning: a gadget that stops getting used after month two is stuck at that first year's $3.75 number, or worse, forever.

What this doesn't capture

This is arithmetic on an estimate, and the estimate is the part that's easy to get wrong — people reliably over-guess how often a new thing will get used. Estimate uses conservatively, and let being wrong in the other direction be the pleasant surprise. It also leaves out resale value, maintenance cost, and storage space, none of which are free either.

Run your own numbers

The free Cost Per Use calculator runs the division instantly from your own price and expected uses — entirely on your device.