Unit Price Calculator
Compare grocery prices per ounce, pound, 100 g, litre or item across sizes, multipacks and coupons, and see which package is the best deal and by what margin.
The interactive tool loads here when JavaScript runs.
About this toolWhat is the Unit Price Calculator?
Enter the price and size of two to eight packages and the Unit Price Calculator works out what each one costs per ounce, pound, 100 grams, kilogram, fluid ounce, gallon, 100 ml, litre or item, ranks them and marks the cheapest. Each runner-up shows how much more it costs per unit in percent and the price it would need to drop to in order to tie.
Multipacks and coupons are handled directly: a twin pack of 28 oz jars is 2 x 28 oz, and a coupon is taken off before dividing. Mix units freely within a kind, such as a 1 kg bag against a 2 lb bag or a 1.75 litre bottle against a gallon jug, and the tool converts with exact factors.
The default compares three jars of peanut butter: 16 oz for 3.29, 40 oz for 6.99 and a twin pack of 28 oz jars for 10.98. The 40 oz jar wins at about 17.5 cents an ounce; the small jar costs 17.7% more per ounce.
- Price per oz, lb, 100 g, kg, fl oz, gallon, 100 ml, litre or item
- Multipacks and coupons included in the calculation
- Exact US and metric conversions from NIST definitions
- Ranking, percentage premium and price needed to tie
- Up to eight items, shareable link, nothing uploaded
How to use the Unit Price Calculator
- For each package, enter its price, the size of one unit and its unit. For a multipack, enter how many units are in the pack.
- Add a coupon or discount amount if you have one; it is subtracted from the price.
- Pick what to compare by (per oz, per 100 g, per litre, per item and so on) and your currency.
- Read the unit price under each package. The best value is outlined in green with a trophy.
- Add up to eight packages, remove extras, then copy the comparison or share a link.
Worked examples
Three jars of peanut butter
Input
16 oz for 3.29; 40 oz for 6.99; 2 x 28 oz for 10.98
Output
0.2056, 0.1748 and 0.1961 per oz; the 40 oz jar wins; the small jar would need to cost 2.80 to tie
The twin pack holds 56 oz but costs 12.2% more per ounce than the single 40 oz jar.
Milk in different units
Input
64 fl oz for 2.49; 1 gallon for 3.99; 1.75 l for 2.19; compare per gallon
Output
4.98, 3.99 and 4.74 per gallon
The gallon jug is cheapest; the half gallon costs 24.8% more per gallon.
A coupon on the bigger box
Input
12 count for 5.49; 30 count for 12.99 with a 2.00 coupon; compare per item
Output
0.458 vs 0.366 per item
With the coupon the 30 count is about 20% cheaper per item; without it, it would be 0.433, still slightly cheaper.
Background and insight
A unit price is just price divided by quantity, scaled to a convenient base. The arithmetic is simple but the traps are not: shelf tags in the same aisle often use different bases (per ounce on one product, per count or per 100 sheets on another), multipacks list the size of one item rather than the pack, and a coupon changes the price but not the quantity.
The tool converts using the exact definitions in US law and NIST Handbook 44: 1 avoirdupois ounce = 28.349523125 g, 1 pound = 16 ounces = 453.59237 g, 1 US fluid ounce = 29.5735295625 ml, and 1 US gallon = 128 fluid ounces = 3.785411784 litres. Ounces measure weight and fluid ounces measure volume, so the calculator refuses to rank a weight-sized package against a volume-sized one rather than pretend they are the same. If a product is sold both ways, compare like with like or convert using the label's weight.
The "price to match" figure is the cheapest unit price multiplied by that package's total quantity, plus any coupon. It answers the practical question at the shelf: how far would this one need to drop before it is as good a deal?
Common use cases
Grocery shopping
Check whether the family size, the store brand or the multipack is really cheaper.
Bulk and warehouse buying
Compare a warehouse pack against regular sizes, including the per-item price of count products.
Online orders
Compare listings that quote sizes in different units, such as grams against ounces.
Small business purchasing
Compare supplier quotes for consumables priced per case, per box or per kilogram.
Tips and limitations
- Bigger is often cheaper per unit, but not always: promotions on small sizes regularly beat the large pack.
- A lower unit price only saves money if you use the product before it expires.
- Compare the same kind of quantity: weight with weight, volume with volume, count with count.
- For products where the useful amount differs, such as concentrated detergent, compare per load or per use instead of per ounce.
Frequently asked questions
How do I calculate unit price?
Divide the price by the quantity, then multiply by the base you want to compare. A 40 oz jar at 6.99 is 6.99 / 40 = 0.1748 per ounce. For a multipack, multiply the size by the number of units first.
Can I compare ounces with fluid ounces?
No. Ounces are weight and fluid ounces are volume, and they only coincide for water-like liquids. The calculator flags a package sized in the other kind of unit instead of ranking it.
Is the biggest package always the cheapest per unit?
No. Larger sizes are often cheaper per unit, but sales on smaller sizes and pricier multipacks reverse that regularly, which is why it pays to check each time.
How do coupons affect unit price?
Subtract the coupon from the shelf price before dividing by the quantity. A 2.00 coupon on a 12.99 box of 30 lowers its unit price from 0.433 to 0.366 per item.
What does "price to match" mean?
It is the price at which that package would cost the same per unit as the cheapest one. If it is far below the shelf price, the cheaper option is a clear win.
How do I compare a kilogram price with a pound price?
Enter both packages in their own units and choose per kg or per lb as the comparison. One pound is exactly 453.59237 g, so a price per pound multiplied by 2.2046 gives the price per kilogram.
Is there an in-depth guide to the Unit Price Calculator?
Yes. “How to Compare Unit Prices and Spot the Real Bargain” covers the background, how it works, common pitfalls and worked examples. Read the full guide.
People also search for
- price per ounce comparison
- which size is the better deal
- unit price per 100 grams calculator
- compare price per item in a multipack
- is the bigger pack cheaper per ounce
- unit price with a coupon
- price per gallon vs half gallon
- cost per kg vs cost per lb
Related Tools You May Like
Free, in-browser tools that pair well with this one.