Free · Shopping & household

Compare Package Prices by Weight, Volume or Item

Compare package prices using a common unit and see which option costs less.

  • Formula & worked example
  • Private in your browser
  • No signup
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Calculator inputs

Enter the values you know

Results update as you type. Edit a result to calculate another value, or lock a value to keep it fixed.

Option A
/
Option B
/
Which one is cheaper?
/
Result

Your calculation

Enter enough known values to calculate the blanks.

Use one currency for your figures. Mixed-currency conversions use rates captured October 5, 2026, rather than live exchange rates.

How to use this calculator

  1. Enter the values you know in the units shown. Leave unknown values blank.
  2. Results update automatically as you type. Edit a result to calculate another value, or lock a value to keep it fixed.
  3. Reset restores the starting fields. A worked example appears below.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

Divide each package's cost by its quantity in the same unit. Bookify compares the values before display rounding, so two prices that look equal to two decimal places can still produce different costs.

Unit price = cost ÷ (quantity per item × item count); savings per unit = |price per unit A − price per unit B|.

Worked example

Enter these known values and leave the other values blank.

Type
Weight
Weight
500 g
Number of items
1
Cost
4 USD
Weight
1000 g
Number of items
1
Cost
6 USD
Price comparison
Option B is cheaper
Unit price
0.01 USD / g
Unit price
0.01 USD / g
You save
0 USD / g

Assumptions and limitations

  • Inputs must satisfy the validation rules. Editing a result can recalculate an earlier input; lock values you want to keep fixed.
  • Currency conversions use the captured source rates from October 5, 2026; they are not live exchange rates.

Common questions

What does this unit price calculation tell me?

Divide each package's cost by its quantity in the same unit. Bookify compares the values before display rounding, so two prices that look equal to two decimal places can still produce different costs.

Can I calculate a different unknown?

Yes. Clear that field and enter the other known values. The calculator uses the available inverse equations.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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