How it works
proportion calculadora — the short version
We built Proportion calculadora because the other tools for this job either cost a subscription or came with a consent banner the size of a small novel.
This is the kind of problem where a stray decimal costs you the mark. Think of one worked example you can reuse — then crunch the numbers and the rest of this page explains what the answer means.
Solve proportions of the form a/b = c/d for any missing term, with direct and inverse proportion worked through step by step.
A worked example, step by step
Consider a realistic scenario and follow it through:
Solve proportions of the form a/b = c/d for any missing term, with direct and inverse proportion worked through step by step.
Scenarios where Proportion calculadora pays off
Proportion calculadora is aimed at people arriving with questions like these:
- "Direct proportion"
- "Inverse proportion"
- "Solve proportion"
- "Proportion formula"
- "What is proportion"
- "How to calculate proportion"
When it isn't the right tool
Every tool has an edge where it stops being the right answer. Proportion calculadora is no exception:
- For legally binding tax or medical decisions — cross-check with HMRC, NHS or a qualified professional.
- For very large or very small extremes the rounding error outgrows the useful precision.
- When the underlying rate or threshold has changed since the page was last reviewed — always verify with the primary source.
- When the input you have is already a derived figure (net of something) — feeding it in as "gross" will double-subtract.
Five things that trip everyone up
Every time you crunch the numbers for a new scenario, one of these creeps in — it's worth knowing them ahead of time.
- Mixing up units — grams in one field, ounces in another, then wondering why the answer is off.
- Treating a percentage as a whole number. 20% means 0.20 in the maths, not 20.
- Rounding at every step. Keep four decimals internally and only round the final number.
- Using last year's thresholds. If the page isn't dated, assume it's stale and check GOV.UK.
- Reading a tool like this as advice. It is maths, not a decision — the decision is still yours.
The sources behind the numbers
Where the maths needs an external authority, we cross-check against:
- BBC Bitesize
- MathsIsFun
Works well alongside
If this question keeps coming up for you, the same cluster of tools usually comes next:
- Ratio calculadora — Simplify ratios, scale them up or down, and split a quantity in a given ratio — ideal for recipes, mixing fluids or sharing costs fairly.
- Rule of Three calculadora — Solve a proportion by cross-multiplication — the classic rule-of-three used for recipe scaling, unit pricing and percent conversions.
- Fraction calculadora — Add, subtract, multiply and divide fractions, convert decimals to fractions, and simplify to lowest terms — with each step shown clearly.
- Percentage calculadora — Work out a percentage of a value, the percentage between two values, and percentage increases or decreases — with the formula shown.
How we keep this accurate
Our calculadoras run on pure, unit-tested functions — the same logic lives in the browser and in the CI test suite. When tax rates, thresholds or official figures move, the update lands within 24 hours of the announcement. You can read the editorial policy and corrections policy.
Found an out-of-date number on Proportion calculadora or anywhere else in the Maths toolkit? Send it to the editorial desk and we'll patch it. Or browse the full calculadora directory for the next tool you need.