How to convert Celsius to Fahrenheit (and Fahrenheit to Celsius)

How to convert Celsius to Fahrenheit is mostly about using the right formula. The exact relationships are:
F = C * 9/5 + 32 and
C = (F - 32) * 5/9. This guide is for anyone who needs quick, correct conversions for weather, cooking, lab work, and everyday comparisons.

If you want to avoid mental math, use the in-browser converter: Celsius ↔ Fahrenheit.

Key takeaways

• Celsius-to-Fahrenheit uses * 9/5 then + 32.
• Fahrenheit-to-Celsius subtracts 32 then multiplies * 5/9.
• Conversions are exact scale formulas; rounding is the only place mistakes happen.
• For precision, round at the end of the calculation (not after each step).

Celsius to Fahrenheit (step-by-step)

Start with a Celsius temperature (C) and plug it into: F = C * 9/5 + 32.

1. Multiply C by * 9/5 (also written as 1.8).
2. Add 32.
3. Round only if you need a whole number (weather and rough estimates often use integers).

Worked examples

Example 1: convert 20 C.
F = 20 * 9/5 + 32 = 36 + 32 = 68 F.

Example 2: convert 0 C.
F = 0 * 9/5 + 32 = 32 F.

Fahrenheit to Celsius (inverse)

Use the inverse formula: C = (F - 32) * 5/9.

1. Subtract 32 from F.
2. Multiply by * 5/9 (also written as 0.555...).
3. Round at the end, if needed.

Accuracy tips (where people slip)

• If you round between steps, you can introduce small but noticeable errors (especially for values like 77 F or 25 C).
• Use consistent units. The formulas assume true Celsius (C) and true Fahrenheit (F), not a local scale or “thermometer style” conversion.

Reference

The Celsius/Fahrenheit temperature scale relationship is documented by NIST.

Next steps

Use the in-browser tool to convert instantly: Celsius ↔ Fahrenheit. Then apply the same “round at the end” approach to other unit conversions.