Sizu Riatto
Kitchen Numbers · Chapter 17

Unit Price Compare, Any Units

Unit price = price ÷ amount, in the same unit for both. Divide by what you’ll actually use, and redo it after a coupon.

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Opens on Chapter 17’s example: Soraya’s two pasta boxes: 1 lb for $1.49 and 500 g for $1.69.

Package A
Package B
Package C (optional)
Enter your numbers, then press Work it out.

How it works

Both packages are converted to one unit using the exact definitions (an ounce is 28.35 g, a pound 453.6 g, a fluid ounce 29.6 mL, a quart 32 fl oz). A coupon comes off the price first. If only part of a package is usable (liquid drained, trimmings, food that spoils), the price is divided by the usable amount, so a third wasted makes each used unit half as dear again. Weight and volume can’t be compared without a density; per cooked cup, divide the price by the cups it makes.

From the book, Chapter 17. Pasta: 32.8¢ per 100 g for the pound box, 33.8¢ for 500 g (17.6 oz). Oats 13.1¢ against 15.5¢ an ounce. Oat milk 5.9¢ against 7.2¢ a fluid ounce ($1.90 and $2.29 a quart). The onion bag is $1.16 a pound, $1.75 a pound used; it wins if you use more than 2.71 lb. Peanut butter with the coupon: 14.3¢ against 17.5¢. Chickpeas: 79.3¢ a cooked cup canned, 31.5¢ from dried. Maple syrup: 35.4¢ a tablespoon. Every chapter and its calculator →

Amounts can be typed as 3, 0.75, 3/4, 1 1/2 or 1½. They’re worked as exact fractions and written as a cook measures them: cups in quarters or thirds, then tablespoons, then teaspoons to the nearest eighth. Everything stays in your browser: no sign-up, nothing stored or sent.