Celsius to Fahrenheit: Formula, Examples & Quick Reference Chart

Converting between Celsius and Fahrenheit comes up constantly — whether you are checking a weather forecast, reading a recipe, or monitoring a patient's temperature. The two scales use different zero points and different step sizes, so the conversion requires both multiplication and addition.

The Formula

To convert Celsius to Fahrenheit, multiply by 9/5 (or 1.8) and then add 32:

°F = (°C × 9/5) + 32

To go the other way — Fahrenheit to Celsius — subtract 32 first, then multiply by 5/9:

°C = (°F − 32) × 5/9

The factor 9/5 comes from the ratio of the Fahrenheit degree size to the Celsius degree size. One Celsius degree spans 1.8 Fahrenheit degrees. The offset of 32 aligns the zero points: 0 °C (water freezes) equals 32 °F.

Quick Mental Trick

For a fast approximation without a calculator, double the Celsius value and add 30:

°F ≈ (°C × 2) + 30

Example: 20 °C → (20 × 2) + 30 = 70 °F. The exact answer is 68 °F — off by just 2 degrees. This trick works well in the everyday temperature range (0–40 °C). It gets less accurate near the extremes.

Worked Example: What is 35 °C in Fahrenheit?

35 °C is a hot summer day or a slightly elevated body temperature. Here is the step-by-step calculation:

1. Start with the formula: °F = (°C × 9/5) + 32
2. Substitute: °F = (35 × 9/5) + 32
3. Multiply: 35 × 9 = 315, then 315 ÷ 5 = 63
4. Add 32: 63 + 32 = 95
5. Result: 35 °C = 95 °F

Similarly, 37 °C (normal human body temperature) = (37 × 9/5) + 32 = 66.6 + 32 = 98.6 °F.

Reference Conversion Table

Why These Temperatures Matter

• 0 °C / 32 °F — water transitions between solid and liquid. Critical for food safety, road conditions, and biology.
• 37 °C / 98.6 °F — average human core body temperature. Readings above 38 °C (100.4 °F) indicate fever.
• 100 °C / 212 °F — water boils at standard atmospheric pressure (sea level). Boiling point drops about 1 °C for every 300 m of altitude.
• Oven temperatures — most baking recipes are written in one scale. A moderate oven is around 180 °C (356 °F); a hot oven is 220 °C (428 °F).
• Weather comfort — temperatures below 0 °C (32 °F) risk frost; above 35 °C (95 °F) pose heat-stress risks without proper hydration.

Adding Kelvin to the Mix

Scientists use the Kelvin scale, which starts at absolute zero — the theoretical point where all molecular motion stops. Converting from Celsius to Kelvin is straightforward:

K = °C + 273.15

So 0 °C = 273.15 K, 100 °C = 373.15 K, and −273.15 °C = 0 K (absolute zero). Kelvin has no negative values and no degree symbol — you write 300 K, not 300 °K.

Need to convert any temperature instantly? Use the DevBench Temperature Converter — it handles Celsius, Fahrenheit, Kelvin, and Rankine in real time.