Unit Price Calculator
Just enter the price and amount. We'll instantly show you which one is the better deal.
Comparing prices when the sizes never match
Shelf prices are designed to be hard to compare: one product is 500 g, the next is 1.2 kg, a third is a "3 for the price of 2" bundle. The only fair way to judge them is the unit price — the cost of a single, common amount such as 100 g or 100 ml. Once every option is expressed that way, the cheapest one is obvious at a glance, regardless of packaging. This calculator does that conversion for two products side by side.
How to enter each product
- Type the price exactly as marked on the shelf.
- Type the amount and pick its unit — g, kg, ml, L, or item. You can mix units between the two products; the tool normalizes them.
- Set items per pack for multipacks. The total amount used in the math is amount × items per pack.
The formula
Unit price = total price ÷ total amount, then scaled to a per-100 figure. Weights are normalized to grams and volumes to millilitres before comparing, so kg vs g and L vs ml line up automatically:
| Given | Equals |
|---|---|
| 1 kg | 1,000 g |
| 1 L | 1,000 ml |
Example 1 — weight, mixed units. Product A costs 1,000 for 500 g; Product B costs 1,800 for 1 kg. A per 100 g = 1,000 ÷ 500 × 100 = 200. B per 100 g = 1,800 ÷ 1,000 × 100 = 180. B is cheaper by 10% per 100 g, even though it costs more on the shelf.
Example 2 — volume. Detergent A is 3.50 for 750 ml; detergent B is 5.00 for 1.5 L (1,500 ml). A per 100 ml = 3.50 ÷ 750 × 100 = 0.467. B per 100 ml = 5.00 ÷ 1,500 × 100 = 0.333. B wins clearly.
Example 3 — a multipack. A single 400 g can costs 1.20 (0.30 per 100 g). A 3-pack of the same 400 g cans costs 3.30, so its total amount is 1,200 g and its unit price is 3.30 ÷ 1,200 × 100 = 0.275 per 100 g — about 8% cheaper per gram.
Reading the comparison
| Product | Price | Amount | Per 100 g |
|---|---|---|---|
| A (single) | 1,200 | 400 g × 1 | 300 |
| B (3-pack) | 3,300 | 400 g × 3 | 275 |
Common mistakes and limits
- Different unit types are not comparable. Weight (g), volume (ml), and count (item) measure different things — enter the same type on both sides, or the "cheaper" answer is meaningless.
- Don't forget the pack count. A bundle looks expensive until you divide by how many items it contains.
- Bigger is not always cheaper. Family sizes sometimes carry a higher unit price than the medium pack — that is exactly what this tool exposes.
- Unit price is only one factor. It ignores quality, brand, and shelf life. The cheapest gram of something you throw away unused is not a saving — buy the size you will actually use.
- Cross-check the shelf label. Many countries require a printed unit price on the tag, but the reference amount can differ (per 100 g here, per kilogram there), so recompute to the same basis before you trust two labels against each other.
Sources & further reading
Frequently asked questions
What is unit price (price per 100g)?
Unit price is a product's total price divided by its total amount — the price per gram, per milliliter or per item. This unit price calculator converts weight and volume products to price per 100g and price per 100ml so they are easy to compare at a glance. Even two products with different sizes can be compared directly once their unit prices line up.
Can it compare kg and g mixed together?
Yes. If one product is in kg and the other in g, the calculator automatically converts both to grams, so the price per unit is accurate. Volume works the same way — L and ml are normalized to ml. Just note that different types of units — weight (g), volume (ml) and count (item) — measure different things and cannot be compared, so enter units of the same type on both sides.
How do I enter a multipack (2+1 etc.)?
Enter the number of items in the items-per-pack field. For example, if a 500g product is sold as a pack of 3 for 9,000, enter amount 500, unit g and items per pack 3. The unit price is calculated from the total amount (amount × items per pack) to tell you which is cheaper.
Is my data sent to a server?
No. The price, amount and other inputs are never sent to a server — everything is calculated inside your browser. Only your last inputs are saved in this browser's localStorage so you can pick up where you left off; nothing is transmitted anywhere else.