Guide
Cost per wear, for watches
It sounds like an accountant's idea of a hobby. It is actually the most honest number a collection can produce — and it rarely says what you expect.
The formula
Cost per wear is what you paid divided by the number of times you have worn it.
Cost per wear = purchase price ÷ number of wears
A £3,000 watch worn 200 times has cost you £15 a wearing. The same watch worn twice has cost you £1,500 a wearing. Nothing about the watch changed. What changed is whether you have actually had the thing you paid for.
A worked example
Take a plausible five-watch collection after one year of logging:
| Watch | Paid | Wears | Per wear |
|---|---|---|---|
| Steel sports watch | £680 | 141 | £4.82 |
| Chronograph | £4,900 | 64 | £76.56 |
| Dive watch | £1,150 | 92 | £12.50 |
| Dress watch | £2,300 | 9 | £255.56 |
| Field watch | £420 | 59 | £7.12 |
Two things fall out of this, and neither is the one people expect.
The first is that the cheap watch is not the bargain — the worn watch is. The steel sports watch and the field watch are close in price, but one of them is doing more than twice the work.
The second is the dress watch. Nine wears in a year is not a failure of the watch; it is a statement about your life. You do not go to nine formal events a year, you go to about nine occasions where you could have worn it and did. That is worth knowing before you buy a second one.
The two mistakes that make the number meaningless
1. Comparing across ages
A watch bought last month will always look terrible on cost per wear next to one you have owned for eight years. The number only compares fairly between watches you have owned for roughly the same time — or when you calculate it over a fixed window, like the last twelve months, for everything at once.
2. Treating it as resale value
Cost per wear is not a valuation and it is not depreciation. A watch you paid £5,000 for and could sell tomorrow for £5,000 has cost you nothing but the opportunity. If you want the fuller picture, use net cost per wear: subtract what you could realistically sell it for today, then divide.
Net cost per wear = (purchase price − current market value) ÷ wears
On that basis a watch that holds its value can be nearly free to wear, and a watch that lost forty percent in two years is expensive whatever the sticker said.
What the number is actually for
Not guilt. The useful version of this exercise is forward-looking: before the next purchase, ask honestly how many days a year you will wear it. Not how many you could. How many you will — given what your existing figures already say about your habits.
Most collectors discover the same thing when they first measure it: two or three watches carry seventy percent of the year, and the rest are rotated in out of duty. That is not an argument for selling everything. It is an argument for buying the next one with your eyes open.
You cannot calculate it without a wear count
Every part of this rests on one number that no receipt and no valuation can give you: how many times you have actually worn the thing. That has to be recorded as it happens. A year of it is the difference between a guess and a figure.
Start counting
Timepiece Log records what you wear each day — watch and strap — and keeps the purchase price alongside it, so the cost-per-wear figure builds itself. Free, browser-based, and your data exports whenever you ask.
Start your log