Cost per use calculator

Cost per unit and per use

Find out what is really cheaper: a big pack or a small one, buying or subscribing, an expensive item that lasts or a cheap one for the season.

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Your numbers · replace with your own

Option 1

Option 2

Option 3

Your result

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An illustration based on the numbers you entered, not a forecast and not advice.

Assumptions & limits

  • Compares price only: it doesn't account for quality, warranty, storage space or whether a large pack goes to waste.
  • Per-use figures assume you keep using the item at the same rate for its whole lifespan.
  • Prices are today's; discounts and price changes over time aren't included.

How it works

Dividing the price by what you actually get

A bigger pack, a pricier product or a subscription can look expensive or cheap until you divide the price by what you actually get. The first mode compares up to three options in the same unit (items, ounces, litres, whatever you type as the unit label) and shows the price per unit and how much more each option costs than the cheapest.

The second mode compares buying with subscribing or renting. It divides the purchase price by the number of uses over the item's lifespan, divides the monthly fee by the uses per month, and finds the month from which buying costs less. If the months you compare outlast one lifespan, the purchase is counted again for each lifespan that fits, rounded up.

Only price is compared. Quality, warranty, storage space and food that goes to waste are not, and the per-use figures assume you keep using the item at the same rate. Prices are today's: discounts and price changes over time are not included. Nothing you enter is stored or sent anywhere.

Formula

Price per unit
unit_cost    = price ÷ quantity
cheapest     = lowest unit_cost among options with quantity > 0
vs_cheapest  = (unit_cost − cheapest) ÷ cheapest × 100

Buy or subscribe
total_uses_buy   = lifespan_years × 12 × uses_per_month
cost_per_use_buy = purchase_price ÷ total_uses_buy
cost_per_use_sub = monthly_fee ÷ uses_per_month
breakeven_months = purchase_price ÷ monthly_fee   (rounded up)
total_buy        = purchase_price × purchases that fit in the months compared
total_sub        = monthly_fee × months compared

Worked example

A 24-pack against a 12-pack, and a $120 purchase against a subscription

A 24-pack costs $12.49 and a 12-pack costs $7.29. Separately, you can buy a $120 item that lasts three years, or pay $9.99 a month; you would use it four times a month and compare 36 months.

Worked example, step by step
Step Result
24-pack, per item $12.49 ÷ 24 = $0.520
12-pack, per item $7.29 ÷ 12 = $0.608, so the 24-pack is 14.3% cheaper per item
Buying, per use $120 ÷ (3 years × 12 × 4 uses) = $0.83
Subscribing, per use $9.99 ÷ 4 uses = $2.50; buying is cheaper after 13 months

Common questions

Is the biggest pack always the cheapest per unit?

Not always. Bigger packs often cost less per unit, but not every time, and the saving only counts if you use all of it. Enter the real prices and quantities to see the difference per unit.

How is the cost per use calculated?

The purchase price is divided by the number of uses over the expected lifespan, which is the lifespan in years times 12 times the uses per month. For a subscription, the monthly fee is divided by the uses per month.

What does the break-even month mean?

It is the purchase price divided by the monthly fee, rounded up. From that month on, what you would have paid in subscription fees is more than the purchase price.

What if I compare more months than the item lasts?

The purchase is counted again for every lifespan that fits into the months you compare, rounded up. A three-year item compared over 48 months is bought twice.

Other ways to ask what it costs you

What a price increase costs you How much a price rise costs per month, per year and over the years ahead. Open calculator → When does it pay off How long a one-off purchase takes to earn back its price through lower running costs. Open calculator → What it costs to run What an appliance or a habit costs per month and per year, and what a replacement saves. Open calculator →

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