Price Per 100g Calculator
Easily compare the true value of products by calculating their unit price. This tool finds the cost per 100 grams, a standard measure used in many stores.
Enter the item's total price and its total weight in grams (g) to see how much it costs per 100g.
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Understanding Unit Price & The Formula
What is Unit Pricing?
Unit pricing breaks down the cost of a product into a standard unit of measurement, like grams, kilograms, or litres. The "price per 100g" is a very common unit price that allows you to make an apples-to-apples comparison between different-sized packages. A larger box might seem cheaper, but its unit price could be higher.
The Price Per 100g Formula
The calculation is straightforward. The tool first finds the price for a single gram, then multiplies it by 100.
Price per 100g = (Total Price / Total Weight in grams) * 100
10 Real-Life Examples
Click on an example to see how unit pricing works in practice.
Example 1: Comparing Breakfast Cereals
Scenario: You're choosing between two boxes of cereal.
- Brand A: Costs £3.00 for a 750g box.
- Brand B: Costs £2.50 for a 500g box.
Calculation for Brand A: (£3.00 / 750g) * 100 = £0.40 per 100g.
Calculation for Brand B: (£2.50 / 500g) * 100 = £0.50 per 100g.
Conclusion: Despite its higher shelf price, Brand A is the better value.
Example 2: A Bag of Potatoes (in kg)
Scenario: A 2.5kg bag of potatoes costs £1.80.
1. Convert Weight: First, convert kilograms to grams. 2.5 kg * 1000 = 2500g.
2. Inputs: Price = 1.80, Weight = 2500.
3. Calculation: (£1.80 / 2500g) * 100 = £0.072 per 100g.
Conclusion: The price is just over 7 pence per 100g.
Example 3: A Small Jar of Spices
Scenario: A jar of paprika costs £1.10 and weighs 45g. Spices often have a very high unit price.
1. Inputs: Price = 1.10, Weight = 45.
2. Calculation: (£1.10 / 45g) * 100 = £2.44 per 100g.
Conclusion: Comparing this value helps you see if buying a larger refill bag is cheaper.
Example 4: Deli Counter Cheese
Scenario: You buy a wedge of cheddar. It weighs 260g and the label says £3.50.
1. Inputs: Price = 3.50, Weight = 260.
2. Calculation: (£3.50 / 260g) * 100 = £1.35 per 100g.
Conclusion: You can compare this to the unit price of pre-packaged cheese to see which is a better deal.
Example 5: Two Jars of Coffee
Scenario: The standard jar is on offer, but is the large jar still better value?
- Standard Jar: Costs £4.00 for 200g.
- Large Jar: Costs £5.50 for 300g.
Calculation (Standard): (£4.00 / 200g) * 100 = £2.00 per 100g.
Calculation (Large): (£5.50 / 300g) * 100 = £1.83 per 100g.
Conclusion: The larger jar is still significantly better value per 100g.
Example 6: Spotting "Shrinkflation"
Scenario: A bag of crisps still costs £1.50, but you think the bag feels lighter than it used to.
- Old Bag: £1.50 for 150g -> (£1.50 / 150g) * 100 = £1.00 per 100g.
- New Bag: £1.50 for 125g -> (£1.50 / 125g) * 100 = £1.20 per 100g.
Conclusion: The unit price has increased by 20%, even though the shelf price hasn't changed. This is "shrinkflation".
Example 7: Bulk Bin Nuts
Scenario: You fill a bag with almonds from a bulk bin. It costs £4.25 and the scale shows it weighs 350g.
1. Inputs: Price = 4.25, Weight = 350.
2. Calculation: (£4.25 / 350g) * 100 = £1.21 per 100g.
Conclusion: Now you can check if this is cheaper than the pre-packaged almonds.
Example 8: Non-Food Item (Face Cream)
Scenario: Unit pricing works for cosmetics too. A tub of face cream costs £12.00 and contains 50g of product.
1. Inputs: Price = 12.00, Weight = 50.
2. Calculation: (£12.00 / 50g) * 100 = £24.00 per 100g.
Conclusion: A very high unit price, common for cosmetics.
Example 9: Pet Food Comparison
Scenario: Comparing a box of wet food pouches with a large bag of dry food.
- Wet Food: A box of 12x100g pouches (total 1200g) costs £9.00.
- Dry Food: A 2kg bag (total 2000g) costs £11.00.
Calculation (Wet): (£9.00 / 1200g) * 100 = £0.75 per 100g.
Calculation (Dry): (£11.00 / 2000g) * 100 = £0.55 per 100g.
Conclusion: The dry food is cheaper per 100g.
Example 10: Liquid Approximation (Olive Oil)
Scenario: A 750ml bottle of olive oil costs £6.00. How does its unit price compare to other oils?
1. Approximation: For many liquids, you can approximate millilitres (ml) as grams (g). So, 750ml ≈ 750g.
2. Inputs: Price = 6.00, Weight = 750.
3. Calculation: (£6.00 / 750g) * 100 = £0.80 per 100g (or per 100ml).
Conclusion: This allows comparison with a 1-litre (1000g) bottle priced at £7.50 (£0.75 per 100g).
10 Frequently Asked Questions
1. Why is "price per 100g" used for comparison?
It's a standard, easy-to-understand unit that allows you to accurately compare the value of two items, regardless of their different packaging sizes or promotional offers.
2. What if the product weight is in kilograms (kg)?
You must convert the weight to grams before entering it. There are 1000 grams in 1 kilogram. Simply multiply the kg value by 1000 (e.g., 1.5 kg = 1500 g).
3. Can I use this for other currencies like dollars ($) or euros (€)?
Yes. The calculator's logic is purely mathematical. Although the label shows a '£' symbol, the calculation will work correctly for any decimal currency. The result will be in that currency (e.g., $0.50 per 100g).
4. What should I do for items sold by volume (millilitres, ml)?
For water-based liquids like juice or milk, the weight in grams is almost identical to the volume in millilitres (1ml ≈ 1g). For these items, you can enter the ml value into the weight field for a very close approximation.
5. Why did I get an error saying "must be greater than zero"?
To perform a meaningful calculation, both the price and the weight must be positive numbers. The calculator shows this error if you enter '0', a negative number, or leave a field blank.
6. Does this work for items sold as a multi-pack?
Yes. You need the total price for the multi-pack and the total weight of all items inside it combined. For example, for a 6-pack of crisps where each bag is 25g, the total weight is 6 * 25g = 150g.
7. What about items sold "by each", like avocados or bread rolls?
This calculator is for items sold by weight. To compare items sold by unit, you would do a different calculation: Total Price / Number of Items. For example, £2.40 for 6 bread rolls is £0.40 per roll.
8. How can I be sure the calculation is correct?
The tool uses the standard, universally accepted formula for unit pricing: (Price / Weight) * 100. The accuracy of the result depends entirely on the accuracy of the numbers you provide.
9. What is "drained weight"? Should I use that?
For items packed in liquid, like tuna or olives, the "drained weight" on the label tells you the weight of the actual food product without the liquid. For the most accurate comparison of the food itself, you should use the drained weight.
10. Can I change the currency symbol?
Yes, if you can edit the code. In the HTML, find the line `` and change the (£). In the JavaScript, find `resultEl.textContent = \`£\${pricePer100g.toFixed(2)}\`;` and change the `£` there as well.
