Floating Point Precision Checker
See the exact value a double stores and how far 0.1 + 0.2 style calculations drift from the decimal answer. Free and private: runs in your browser.
Enter a number or simple expression to compare the floating-point result with the exact decimal result.
Numbers are checked locally in your browser and never sent anywhere. Use test data, not real customer details.
Use cases
- Validate test data for payment and banking flows.
- Catch typos in account and card details before calling a provider API.
- Explain money-handling rules to your team with real examples.
Frequently asked questions
Why does 0.1 + 0.2 equal 0.30000000000000004?
Doubles store binary fractions. 0.1 and 0.2 are rounded to the nearest binary value, and their sum rounds to a number just above 0.3.
Is the Floating Point Precision Checker free?
Yes. It is free with no sign-up, and it runs entirely in your browser, so your input is never uploaded or stored.
Can I use real customer data here?
Avoid it. Everything runs locally, but good practice (and PCI DSS) is to use test data outside production systems.
Related tools
Checking one snippet is a start. Scan your whole repository for free with CodeInspector.