Recipe Scaler

A recipe scaler adjusts ingredient quantities when you want to make more or fewer servings than a recipe specifies. Whether you are doubling a cookie recipe for a party, halving a soup recipe for two people, or converting a restaurant recipe that serves fifty down to a family portion, scaling manually is error-prone — especially with fractions and mixed units. This tool handles the math automatically: enter the original serving count, your desired serving count, and each ingredient with its quantity and unit. The scaler calculates the exact ratio and applies it to every ingredient instantly. It handles fractions gracefully (turning 1/3 cup into 2/3 cup when doubling), converts between metric and imperial units when helpful, and flags ingredients that do not scale linearly (like yeast, baking powder, or seasoning). Everything runs in your browser using JavaScript arithmetic, so your recipe data is never uploaded to any server.

The core scaling calculation divides the desired serving count by the original serving count to produce a multiplier. Each ingredient quantity is then multiplied by this factor. For example, scaling from 4 servings to 6 gives a multiplier of 1.5, so 2 cups of flour becomes 3 cups. The tool represents quantities internally as decimal numbers for precision, then converts back to friendly fractions for display using a greatest-common-divisor algorithm — so 0.333 becomes 1/3 and 0.667 becomes 2/3 rather than showing unwieldy decimals. For mixed numbers, it separates the whole and fractional parts. The unit conversion layer recognizes relationships between common cooking measurements (3 teaspoons per tablespoon, 16 tablespoons per cup, 2 cups per pint) and suggests unit changes when the scaled quantity would be more practical in a different unit. All processing happens locally using pure JavaScript — no APIs, no server requests, and no data stored unless you explicitly save to your browser localStorage.