How do I work out what something costs per use?

Cost per use answers a question price cannot: is this good value for me? A £400 machine used daily for eight years costs pennies a use. A £40 gadget used twice costs £20 a time. It also reframes the buy-or-hire question, the buy-cheap-or-good question and the keep-or-sell question, all of which turn on how often the thing is actually used.

Step by step

1. Work out the whole-life cost first.Purchase plus running costs, consumables, servicing and disposal, minus resale value. Price alone understates the cost of anything with consumables and overstates the cost of anything that holds value.
2. Estimate uses honestly, then halve it.Pre-purchase estimates of how often something will be used are systematically optimistic. If you already own something similar, count actual uses over the last year rather than guessing.
3. Divide, and compare with the alternative per use.The comparison is what makes the number useful: cost per use against hiring per use, against paying someone per job, against doing without. A number on its own is not a decision.
4. Apply it to things you already own.Run it across the appliances, tools and equipment in the house. The results usually identify two or three items that are worth selling and one or two where buying a better version is clearly justified.
5. Use it on the buy-or-hire question.If hire costs a fraction of the purchase and you will use it a handful of times, hiring wins comfortably — and you get a serviced, current tool rather than storing a neglected one.
6. Include storage where it is genuinely scarce.In a small home, the space a rarely used item occupies has real value. It does not need a precise figure, but it belongs in the judgement.

Tips

• Cost per use makes the case for spending more on things used daily as clearly as it makes the case against buying things used yearly.
• For shared items — a household drill, a wallpaper stripper, a carpet cleaner — cost per use across several households can turn a bad purchase into a sensible one.
• Apply it to subscriptions by dividing the annual cost by the number of times you actually used the service, not by the number of months you paid for.

Common mistakes

• Counting intended uses rather than likely ones — The intention is the thing being sold to you. Use your own history with similar items, which is the only evidence that predicts your behaviour.
• Ignoring running costs in the numerator — For anything using energy or consumables, the running cost frequently exceeds the purchase price over the life, and leaving it out reverses conclusions.

Questions people ask