Skip to content

    Under active development. New calculators and features ship every week. Everything currently runs free while the site matures — pricing pages are a preview, checkout is not open yet.

    Search ⌘K
    Calculates locally in your browser · normalised price comparison
    Consumer / value comparison

    Unit price comparison

    Compare two packages of different sizes on price per unit — the only measure that ranks them fairly. The page also prices the quantity you actually need, because a cheaper unit price can still cost more when it forces you to buy extra packages.

    Unit gap0.30 ¢Need3000Leftover A0
    Unit price A
    1.298 ¢
    $6.49 for 500
    Unit price B
    0.999 ¢
    $11.99 for 1200
    Cheaper option
    Package B
    23.02% cheaper per unit
    Saving on your need
    $8.96
    For 3000 units
    Unit-price comparison
    Both packages normalised to the same unit, plus the cost of buying exactly what you need.
    B is cheaper per unit
    Unit-price comparison
    OptionPriceSizePrice per unitCost for the need
    Package A$6.495001.298 ¢$38.94
    Package B$11.9912000.999 ¢$29.98
    Difference$5.507000.299 ¢$8.96

    Unit price is the only fair comparison. Package size, not price, is what most shoppers misjudge — a larger box is often the more expensive option per unit.

    Inspect the model
    Choose a quick result view, a scaled comparison, or the complete diagnostic set.
    Price per unit
    The normalised comparison — the only number that ranks the packages.
    Price per unit0.0000.3060.6130.9191.231.531.30Package APackage A0.999Package BPackage B¢ per unit
    Total cost for the quantity you need
    Package A wins at small quantities; the cheaper unit price wins as the need grows.
    Total cost for the quantity you need$0$9$17$26$35$4425025050050075075010001000150015002000200030003000Package APackage B
    Canonical equations
    The exact relationships implemented by this engine.

    p / q · price divided by package size

    (dear − cheap)/dear · per-unit advantage of the cheaper option

    (need/q)·p · ignores leftover product

    ⌈need/q⌉·q − need · units you buy but do not use

    finance methodology

    A clear path from inputs to results.

    Package sizes are designed to make comparison hard. Price per unit is the only measure that ranks them fairly, and even then the cheaper unit price can cost more if it forces you to buy more than you need.

    Step-by-step methodWorked exampleAssumptions explained

    How to use

    1. Enter the price and size of the first package.
    2. Enter the price and size of the second.
    3. Read both unit prices — the comparison is now honest.
    4. Enter the quantity you actually need.
    5. Check the leftover, because rounding up to whole packages changes the answer.

    The formula

    u=pq,saving=udear−ucheapudear,waste=⌈n/q⌉q−nu = \frac{p}{q}, \qquad \text{saving} = \frac{u_{\text{dear}} - u_{\text{cheap}}}{u_{\text{dear}}}, \qquad \text{waste} = \lceil n/q \rceil q - n

    Reference: Unit-pricing disclosure rules (EU 98/6/EC; US state unit-pricing statutes).

    Worked example

    $6.49 for 500 units vs $11.99 for 1,200

    Inputs
    • Package A: $6.49 for 500.
    • Package B: $11.99 for 1,200.
    • Need 3,000 units.
    Calculation path
    1. 1

      Unit price A: 6.49 / 500 = 1.298¢.

    2. 2

      Unit price B: 11.99 / 1,200 = 0.999¢.

    3. 3

      B is 23.0% cheaper per unit.

    4. 4

      Cost for 3,000: A = $38.94; B = $29.98.

    5. 5

      Both divide evenly, so there is no leftover to weigh against the saving.

    Result

    B is 23% cheaper per unit and saves $8.96 on the quantity needed.

    Interpreting the result

    The larger package usually wins per unit, but not always — multipacks and “family size” reprints are sometimes priced above the smaller pack. And a cheaper unit price only pays if you will use the quantity; for perishables, the leftover is a real cost that the per-unit comparison ignores.

    Assumptions & limitations

    • Both packages contain an identical product; quality and brand are not priced.
    • Sizes are in the same unit. Mixed units must be converted first.
    • No storage, spoilage or financing cost is attached to buying more than needed.
    • Discounts and coupons are already reflected in the entered prices.

    Frequently asked questions

    Why is the bigger package sometimes more expensive per unit?

    Because packaging, shelf position and convenience carry their own price. Multipacks are not always discounted, and smaller “convenience” sizes can be priced at a premium or a discount depending on the retailer’s strategy.

    How do I compare different units?

    Convert both to a common base first — grams, millilitres or count. Comparing price per ounce with price per 100 g without converting is the classic error.

    Does the cheaper unit price always win?

    Only if you use the quantity. If package B is cheaper per unit but you need 300 units and it contains 1,200, you have paid for 900 units you may never use.

    Should I use price per unit or total price?

    Unit price for ranking, total price for the decision. The decision also has to account for how much you will actually consume.

    Methodology last reviewed 2026-10-18. Results are informational and not financial or engineering advice — see our disclaimer.