Ratio Calculator · Practical guide
How to Scale a Recipe Using Ratios
Hold the ingredient ratio constant, change one amount, and solve the proportion for the rest.
At a glance
Quick answer
To scale a recipe with ratios, keep the ingredient ratio constant and solve a proportion for the new amounts. If a recipe uses flour and sugar in a 3 : 2 ratio and you want to use 600 g of flour, set up 3 : 2 = 600 : x — cross-multiply to get 3x = 1,200, so x = 400 g of sugar. Enter A = 3, B = 2, C = 600 above and leave D blank to confirm.
Interactive tool
Ratio Calculator
Enter your own values, then compare the result with the examples below.
Proportion: A : B = C : D (leave one field blank to solve)
Result
Flour-to-Sugar Scaling at 3 : 2
| Flour | Sugar | Total batch |
|---|---|---|
| 300 g | 200 g | 500 g |
| 450 g | 300 g | 750 g |
| 600 g | 400 g | 1,000 g |
| 750 g | 500 g | 1,250 g |
Why Ratios Beat Multiplying
Recipes rarely scale by a clean factor — you have 600 g of flour left, not exactly double. Working from the ratio handles any starting amount: each part of the 3 : 2 mix is 600 ÷ 3 = 200 g, so sugar is 2 × 200 = 400 g and the batch totals 1,000 g. The scale factor, shown by the calculator, is 600 ÷ 3 = 200 per part.
Scaling the Whole Recipe
Once you know the value of one part, every ingredient follows. For a 3 : 2 : 1 blend of flour, sugar, and butter scaled to 600 g of flour, one part is 200 g, so sugar is 400 g and butter is 200 g. Run each ingredient through the proportion separately: A = original amount, B = original flour, C = new flour, and solve for D.
Cutting a Recipe Down
The same math halves or thirds a batch. A 3 : 2 recipe built on 900 g of flour needs 600 g of sugar; scaling to 450 g of flour (half) gives sugar = (2 × 450) ÷ 3 = 300 g. Ratios hold in both directions — that is the whole point of a proportion.
Frequently Asked Questions
Can I scale a recipe by any amount?
Yes — the ratio method works for any scaling factor, including awkward ones like 1.7×. Solve the proportion with your new key-ingredient amount and every other ingredient follows.
Do cooking times scale with the recipe?
Not proportionally. A doubled batch often needs only slightly more time, and pan depth matters more than quantity. Scale ingredients by ratio, but adjust time by observation.
Should I use weight or volume for scaling?
Weight (grams) is far more reliable — a cup of flour can vary by 20% depending on how it is scooped, while 600 g is always 600 g.
What if my recipe ratio has decimals, like 1 : 0.67?
The calculator accepts decimals directly. For flour to milk at 1 : 0.67 with 500 g of flour, solve 1 : 0.67 = 500 : x to get 335 g of milk.