How we check our math

Every answer and every step on qcalculate comes from the same exact calculation, and it is tested before it goes live.

Exact arithmetic, not floating point

Most software stores numbers in a binary format that can't hold values like 0.1 exactly. That is why some calculators show 0.1 + 0.2 = 0.30000000000000004. qcalculate stores every number as an exact fraction, so 0.1 + 0.2 is exactly 0.3, and 33% of 1/3 is exactly 0.11.

Steps come from the calculation itself

The steps you see are produced by the same code that calculates the answer, using your numbers. They are never generated by AI: AI language models can make arithmetic mistakes, so we never use them to calculate.

Every calculator is tested

Before a calculator goes live, it is checked against:

• answers worked out by hand;
• tricky cases such as zero, negative numbers, very large numbers and fractions;
• its own other modes. For example, the percentage calculator checks that "15% of 200 is 30" and "30 is 15% of 200" always agree.

These tests run automatically every time the site is updated, and an update is blocked if any test fails.

How we round

• Answers are shown exactly when they have 10 decimal places or fewer.
• Answers whose decimals never end, like 1 ÷ 3 = 0.333…, are rounded for display and marked with ≈. The working behind them stays exact.
• Halves are rounded away from zero, the way most people learn at school: 2.5 becomes 3.
• Percentages are shown with up to 4 decimal places.

What you can type

Numbers can include commas (1,234.5 or 12,34,567), fractions (3/4 or 2 1/2), a % sign where it makes sense, and digits written in Bengali, Arabic or Hindi. If something is unclear, like "1,5", the calculator asks you to use a dot for decimals instead of guessing.

Limits

qcalculate's answers are for learning and general information. For decisions about money, health, law or safety, check with a qualified professional. See the disclaimer.

Found a mistake?

Please tell us. Click Copy share link on the calculator, which saves your numbers in the link, and send it to us through the contact page. We fix confirmed mistakes as quickly as we can.