Celsius to Fahrenheit Converter
Quick Conversion: F = (C × 9/5) + 32
Celsius to Fahrenheit Converter
What Is Celsius?
The degree Celsius (°C) is the SI-derived unit of temperature. It sets the freezing point of water at 0°C and the boiling point at 100°C. Invented by Swedish astronomer Anders Celsius in 1742, it is the most widely used temperature scale worldwide for weather, cooking, science, and everyday measurement.
What Is Fahrenheit?
The degree Fahrenheit (°F) is the primary temperature unit in the United States. Water freezes at 32°F and boils at 212°F — exactly 180 degrees apart. Devised in 1724 by Daniel Gabriel Fahrenheit, it remains standard in the US for weather forecasts, cooking recipes, and medical thermometers.
Celsius to Fahrenheit Formula
The formula is:
°F = °C × 9/5 + 32 exact
This offset formula means you multiply first, then add — unlike simple unit conversions. The factor 9/5 (= 1.8) accounts for the different degree sizes, and +32 shifts to the Fahrenheit zero point.
Worked Example
Convert 37°C (normal body temperature) to Fahrenheit:
- Multiply: 37 × 9/5 = 66.6
- Add offset: 66.6 + 32 = 98.6°F
So 37°C = 98.6°F — the classic body temperature value recognized worldwide.
Quick Estimation
For mental math: double the Celsius value and add 30. Example: 25°C → 25 × 2 + 30 = 80°F (exact: 77°F). This shortcut is accurate within ±2°F for the 0–40°C range — good enough for weather and everyday use. It works because 2 ≈ 9/5 and 30 ≈ 32.
Reference Table
Weather
| °C | °F | Conditions |
|---|---|---|
| −40 | −40 | Extreme cold (scales equal) |
| −20 | −4 | Severe winter |
| 0 | 32 | Freezing point of water |
| 10 | 50 | Cool — jacket weather |
| 20 | 68 | Comfortable room temperature |
| 25 | 77 | Warm summer day |
| 30 | 86 | Hot — beach weather |
| 40 | 104 | Heat wave / extreme heat |
Body Temperature
| °C | °F | Meaning |
|---|---|---|
| 36.1 | 97 | Low normal |
| 37 | 98.6 | Classic normal body temperature |
| 38 | 100.4 | Fever threshold (WHO/CDC) |
| 39 | 102.2 | Moderate fever |
| 40 | 104 | High fever — seek medical attention |
Cooking
| °C | °F | Use |
|---|---|---|
| 150 | 302 | Low oven / slow roasting |
| 180 | 356 | Standard baking (cakes, bread) |
| 200 | 392 | Roasting vegetables, chicken |
| 220 | 428 | Pizza, high-heat roasting |
| 250 | 482 | Broiling / grilling |
When You Need This Conversion
- Travel to the US: Weather forecasts, road signs, and thermostats use Fahrenheit. Knowing that 20°C = 68°F helps you interpret "highs in the low 70s" as comfortable.
- Cooking with American recipes: US recipes specify oven temperatures in °F. A European cook setting 180°C needs to know that's 356°F — close enough to the "350°F" standard in most US recipes.
- Medical communication: A doctor in Europe reading 38°C knows it's a fever; telling a US nurse requires saying 100.4°F. The fever threshold — 38°C / 100.4°F — is a critical value to know.
Frequently Asked Questions
What is 37°C in Fahrenheit?
37°C = 98.6°F. This is the traditional normal human body temperature, established by Carl Wunderlich in 1868. Modern studies suggest the average is slightly lower, around 36.6°C (97.9°F).
Is 38°C a fever?
Yes. 38°C (100.4°F) is the standard fever threshold used by the WHO and CDC. A temperature above 38°C in an adult is considered a fever; above 39.4°C (103°F) is a high fever requiring medical attention.
What is 0°C in Fahrenheit?
0°C = 32°F. This is the freezing point of water — the temperature at which liquid water becomes ice at standard atmospheric pressure.
Why is "double and add 30" only approximate?
The exact formula is °F = °C × 9/5 + 32. The shortcut replaces 9/5 (1.8) with 2 and 32 with 30. At 0°C the error is −2°F; at 37°C the error is +4.6°F. It is accurate within ±5°F for the 0–50°C range — useful for quick estimates, not for cooking or medical precision.
At what temperature are Celsius and Fahrenheit equal?
At −40 degrees — the only point where both scales give the same number. Set °C = °F in the formula: °F = °F × 9/5 + 32, solve for °F = −40.
Temperature conversion chart
| To Fahrenheit | To Celsius | To Kelvin | |
| From Fahrenheit (F) | F | (F - 32) × 5/9 | (F - 32) × 5/9 + 273.15 |
| From Celsius (C or o) | (C × 9/5) + 32 | C | C + 273.15 |
| From Kelvin (K) | (K - 273.15) × 9/5 + 32 | K - 273.15 | K |
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All unit conversions on CoolConversion use conversion factors defined or documented by internationally recognised standards bodies (such as ISO and NIST), including both SI and non-SI units.
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