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    Unit Price Calculator

    Compare unit prices to find the best deal. Add multiple products and see which offers the lowest cost per unit.

    Free to use. Runs in your browser.

    Enter two product sizes and prices to see which is better value per unit. Works with grams, kilos, ounces, millilitres, fluid ounces, or pieces.

    Unit Price Comparison

    Why Unit Price Is the Only Number That Matters

    A 500g bag of rice for £1.20 vs a 1kg bag for £2.10, which is cheaper? Your instinct says the bigger bag, but the maths says the smaller one. The 500g bag costs £2.40/kg. The 1kg bag costs £2.10/kg. The larger pack wins by 30p per kilo.

    Supermarkets are legally required to show unit prices on shelf labels in the UK. But the labels are often in different units (per 100g vs per kg), tiny print, or missing entirely online. This calculator normalises everything so you can compare properly.

    The biggest savings come from comparing across brands and pack sizes. Own-brand products are typically 20-40% cheaper per unit than branded equivalents. But not always, check, don't assume.

    Real Supermarket Comparisons

    Here's how unit pricing reveals the actual best deal (typical UK prices):

    ProductPack PriceSizeUnit PriceWinner?
    Branded cereal£3.50500g£7.00/kgNo
    Own-brand cereal£1.20500g£2.40/kgYes, 66% cheaper
    Small washing-up liquid£1.00450ml£2.22/litreNo
    Large washing-up liquid£1.50900ml£1.67/litreYes, 25% cheaper

    Supermarket Tricks to Watch For

    Trick

    Unit switching

    One product shows price per 100ml, the next per litre, a third per item. This makes mental comparison nearly impossible, which is exactly the point. Always normalise to the same unit.

    Trick

    "Family size" premium

    Larger packs are usually cheaper per unit, but not during promotions. Supermarkets sometimes discount the medium pack below the bulk unit price. Always check, don't assume bigger is better.

    Trick

    Shrinkflation

    Same price, smaller pack. A chocolate bar that used to be 200g is now 180g at the same price. That's an 11% price increase disguised as "new look, same great taste." Unit pricing catches this instantly.

    Smart Shopping Tips

    • Factor in waste. A 2kg bag of salad at half the per-gram price is no bargain if half ends up in the bin. Buy quantities you'll actually consume.
    • Consider performance, not just price. A £3 bottle of detergent that lasts twice as long as a £2 one is better value per wash. Unit price per use matters more than unit price per gram for some products.
    • Compare across stores. The cheapest option in one supermarket might be more expensive than the mid-range in another. Unit price lets you compare across stores on equal terms.

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    How to use this tool

    1

    Enter the price and quantity for each product

    2

    Set the unit of measurement

    3

    The best value is highlighted automatically

    Common uses

    • Comparing supermarket products of different sizes
    • Finding the best value across different brands
    • Checking whether multi-buy offers are genuine deals
    • Comparing prices across different shops
    • Working out whether bulk buying saves money

    Share this tool

    Frequently Asked Questions

    What is unit price?
    Unit price is the cost per single unit of measure, price per gram, per litre, or per item. It normalises products of different sizes so you can compare them fairly. The lowest unit price is the best value, regardless of pack size.
    How do I use this calculator?
    Add two or more products with their price and quantity. Select the unit of measurement. The calculator instantly finds the lowest unit price and highlights the best value with a trophy icon.
    Does it work for any unit?
    Yes, grams, kilograms, millilitres, litres, ounces, pounds, or items. The key is being consistent: compare all products in the same unit. Don't mix grams and kilograms.
    Is the bigger pack always cheaper per unit?
    Usually, but not always. Supermarkets sometimes price medium packs more aggressively during promotions. Multi-buy deals can also make smaller packs cheaper per unit. Always check, your assumptions may cost you money.
    Why do supermarket labels show different units?
    One product shows price per 100ml, another per litre, a third per wash. This inconsistency makes mental comparison nearly impossible, which arguably benefits the retailer. This calculator normalises everything to the same unit.
    Should I always buy the cheapest per unit?
    Not necessarily. Consider waste (will you use it all before it expires?), storage space, quality differences, and whether you actually need that much. A bulk pack is only a deal if you consume it all.
    Are own-brand products better value?
    Typically 20-40% cheaper per unit than branded equivalents. In many cases, own-brand products are made in the same factories as branded ones. But not always, some categories (like certain cleaning products) have genuine quality differences.
    How do I compare products with different units?
    Convert to the same unit first. For weight: 1kg = 1,000g. For volume: 1L = 1,000ml. For imperial/metric: 1oz ≈ 28.35g, 1lb ≈ 453.6g. Use the same unit for all products in a comparison.
    Does unit price include VAT?
    In UK supermarkets, shelf prices include VAT. So the unit price comparison is valid as-is. For trade or wholesale comparisons, make sure all prices either include or exclude VAT consistently.
    What about price per wash or per use?
    Some products (like laundry detergent) are better compared by 'price per use' rather than price per gram. A concentrated product weighs less but does the same number of washes. Check the 'number of uses' on the label when available.
    Can I compare across different shops?
    Yes, that's one of the best uses. Enter the same product from Tesco, Sainsbury's, and Aldi with their respective prices and pack sizes. The calculator shows you which shop offers the best value per unit.
    How much can I save by comparing unit prices?
    Studies suggest the average UK household could save £500-1,000 per year by consistently choosing the best unit price. The savings are biggest on frequently purchased items like cereal, washing-up liquid, and snacks.
    Is unit pricing required on US, Canadian, and Australian shelves?
    Rules vary. In the US, 21 states mandate unit price labels, California, New York, New Jersey and others, while the rest leave it voluntary. In Canada, Quebec mandates unit pricing in supermarkets over 375m²; other provinces make it optional. In Australia, the ACCC's Grocery Unit Pricing Code requires all large supermarkets to show unit prices on shelves and in online catalogues. Your eyes still need this calculator when units are inconsistent.
    Which aisles benefit most from unit-price comparison?
    Across the UK, US, Canada and Australia the biggest wins come from cereal, pasta, rice, laundry detergent, toilet roll, cleaning sprays, nappies/diapers, pet food, and supermarket tea or coffee. These are categories where shelf units shift between grams, kilos, ounces, pounds and 'per use', making mental comparison unreliable.
    Does unit price matter for halal and kosher-certified products?
    Yes. Halal meat, dairy and pantry staples often carry a certification premium. Comparing unit price across brands (for example, Tayyib-certified vs standard halal) reveals whether you're paying for the certification, the sourcing, or just the packaging. Many Muslim UK, US, Canadian and Australian households save meaningfully by switching to larger halal bulk packs from specialist grocers.

    Results are for general informational purposes only and should be checked before use. They are not professional advice. See our Disclaimer and Terms of Service.