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Fahrenheit and Celsius measure temperature on scales with different zero points and different degree sizes, so converting takes both a subtraction and a multiplication. This tool applies the formula, turning Fahrenheit into Celsius and back.
Fahrenheit to Celsius Converter: step-by-step worked example
What is a 100 °F heat wave in Celsius?
- Value
- 100
- Direction
- Fahrenheit → Celsius
- 1
Scale factor
Water freezes at 0 °C / 32 °F and boils at 100 °C / 212 °F → 180 ÷ 100 = 9/5
(212 − 32) ÷ (100 − 0) = 1.8 = 1.8
- 2
First operation
°C → °F: °C × 9/5 · °F → °C: °F − 32
100 − 32 = 68
- 3
Result
°F = °C × 9/5 + 32 · °C = (°F − 32) × 5/9
68 × 5 ÷ 9 = 37.7778 °C
- 4
Check (reverse direction)
Convert the result back with the other formula
37.7778 × 9 ÷ 5 + 32 = 100 °F
- Below freezing
- Cold–cool
- Mild–warm
- Body temp.
- Fever
- Below boiling
- Above boiling
- Water freezes (0 °C)32 °F
- Room (20 °C)68 °F
- Body (37 °C)98.6 °F
- This example100 °F
- Water boils (100 °C)212 °F
Good to know: Quick estimate: °C × 2 + 30 ≈ °F (a few degrees off at everyday temperatures). −40 is the same in both scales; normal body temperature is 37 °C = 98.6 °F.
Fahrenheit to Celsius Converter — how it works
The conversion factor
Temperature needs an offset as well as a scale factor:
| Direction | Formula |
|---|---|
| °F → °C | (°F − 32) × 5/9 |
| °C → °F | (°C × 9/5) + 32 |
The two scales meet at −40°, where they read the same.
Common values
| Fahrenheit | Celsius |
|---|---|
| 32 °F | 0 °C |
| 68 °F | 20 °C |
| 98.6 °F | 37 °C |
| 212 °F | 100 °C |
Worked example
A 72 °F room is (72 − 32) × 5/9 = 22.2 °C. A 100 °F fever is (100 − 32) × 5/9 = 37.8 °C. Water freezes at 32 °F / 0 °C.
Celsius to Fahrenheit table
| °C | °F |
|---|---|
| -40 | -40 |
| -20 | -4 |
| -10 | 14 |
| 0 | 32 |
| 5 | 41 |
| 10 | 50 |
| 15 | 59 |
| 20 | 68 |
| 25 | 77 |
| 30 | 86 |
| 35 | 95 |
| 36.6 | 97.9 |
| 37 | 98.6 |
| 38 | 100.4 |
| 39 | 102.2 |
| 40 | 104 |
| 50 | 122 |
| 100 | 212 |
Fahrenheit to Celsius table
| °F | °C |
|---|---|
| 0 | -17.8 |
| 32 | 0 |
| 50 | 10 |
| 68 | 20 |
| 77 | 25 |
| 86 | 30 |
| 98.6 | 37 |
| 100 | 37.8 |
| 104 | 40 |
| 212 | 100 |
Frequently asked questions
How do I convert Fahrenheit to Celsius?+
Subtract 32, then multiply by 5/9. For example, 50 °F = (50 − 32) × 5/9 = 10 °C. A rough estimate is “subtract 30 and halve”.
How do I convert Celsius to Fahrenheit?+
Multiply by 9/5 (1.8) and add 32. So 25 °C = 25 × 1.8 + 32 = 77 °F.
Why do I subtract 32 first?+
Because the scales have different zero points: 0 °C equals 32 °F. Removing the 32-degree offset lines the scales up before applying the 5/9 size ratio.
What is 100°F in Celsius?+
100 °F is 37.8 °C — just above normal body temperature, which is why it registers as a mild fever.
At what point are °F and °C equal?+
At −40°. Minus 40 Fahrenheit equals minus 40 Celsius, the single temperature where both scales agree.
About this page
- Publisher:
- Kalkoro — Teknolojig Bilişim Teknolojileri A.Ş., İstanbul
- Written by:
- Ahmet Tur — Editor (Math, date & time, unit conversion, physics & chemistry, everyday tools)
- Reviewed by:
- Kübra Yıldız — Editor
Parameters come from official sources; the last update date is shown at the bottom of the page.
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