Proportion Calculator
Proportion Calculator
A proportion states that two ratios are equal, written as A/B = C/D, and solving for a missing term is a skill that comes up constantly in everyday scaling problems — from resizing a recipe to reading a map. Enter the three values you know, choose which term is missing, and this calculator solves for it using cross-multiplication. It's a quicker, more reliable alternative to setting up and solving the equation by hand every time a new proportion problem comes up.
- Cross-multiplication formula: A × D = B × C, rearranged to solve for whichever term is unknown.
- Example: if 2/3 = 10/D, cross-multiplying gives 2D = 30, so D = 15.
- Common uses: scaling recipes, converting map distances to real distances, and solving similar-triangle geometry problems.
What does "Solve For" mean here?
Select which of the four terms (A, B, C, or D) you want the calculator to find — its own input value is then ignored and only used to label the field.
Can I use this for recipe scaling?
Yes — e.g. if a recipe for 4 servings needs 2 cups of flour, set up 4/2 = (new servings)/D to find how much flour you need for a different serving size.
Proportion Calculator
A proportion states that two ratios are equal, written as A/B = C/D, and solving for a missing term is a skill that comes up constantly in everyday scaling problems — from resizing a recipe to reading a map. Enter the three values you know, choose which term is missing, and this calculator solves for it using cross-multiplication. It's a quicker, more reliable alternative to setting up and solving the equation by hand every time a new proportion problem comes up.
- Cross-multiplication formula: A × D = B × C, rearranged to solve for whichever term is unknown.
- Example: if 2/3 = 10/D, cross-multiplying gives 2D = 30, so D = 15.
- Common uses: scaling recipes, converting map distances to real distances, and solving similar-triangle geometry problems.
What does "Solve For" mean here?
Select which of the four terms (A, B, C, or D) you want the calculator to find — its own input value is then ignored and only used to label the field.
Can I use this for recipe scaling?
Yes — e.g. if a recipe for 4 servings needs 2 cups of flour, set up 4/2 = (new servings)/D to find how much flour you need for a different serving size.