Celsius to Fahrenheit Converter
This calculator converts a temperature in degrees Celsius into its exact equivalent in Fahrenheit, using the standard formula F equals C times nine fifths plus 32, which is handy whenever you meet a US weather forecast, an oven manual, a recipe, or a scientific reading given in a scale you are not used to. Enter a value into the Celsius field and the Fahrenheit result updates instantly, or enter a Fahrenheit value instead and the Celsius field updates in reverse, since editing either input recalculates the other automatically. You can also choose how many decimal places to show, from a whole number up to four decimal places, for cases where extra precision matters. Alongside the headline result, the calculator returns the same temperature in Kelvin and Rankine, a breakdown of the calculation steps for both directions, and a plain-language verdict describing where your figure sits, such as freezing, body temperature or boiling point. A reference table further down lists common temperatures, from absolute zero to the boiling point of water, with Celsius, Fahrenheit and Kelvin shown side by side, so you can check a familiar landmark without doing any maths. Because the conversion follows a fixed, internationally agreed formula rather than an estimate, the figure returned is exact, so you can rely on it for cooking, travel, health readings and everyday comparisons between the metric and imperial temperature scales.
1. Celsius to Fahrenheit
2. Fahrenheit to Celsius (Reverse)
Editing either field updates the other automatically.
Common Reference Temperatures
| Reference Point | Celsius (°C) | Fahrenheit (°F) | Kelvin (K) |
|---|---|---|---|
| Absolute zero | -273.15 | -459.67 | 0 |
| Water freezes (at sea level) | 0 | 32 | 273.15 |
| Cold winter day | -10 | 14 | 263.15 |
| Cool room | 16 | 60.8 | 289.15 |
| Comfortable room temperature | 20 | 68 | 293.15 |
| Warm day | 30 | 86 | 303.15 |
| Body temperature (normal) | 37 | 98.6 | 310.15 |
| Hot summer day | 40 | 104 | 313.15 |
| Celsius = Fahrenheit | -40 | -40 | 233.15 |
| Water boils (at sea level) | 100 | 212 | 373.15 |
Calculation Steps (C to F)
Calculation Steps (F to C)
How to Convert Celsius to Fahrenheit
The formula to convert Celsius (C) to Fahrenheit (F) is:
F = (C × 9/5) + 32
This formula works by first scaling the Celsius value to match the size of a Fahrenheit degree (there are 180 Fahrenheit degrees between freezing and boiling, versus 100 Celsius degrees, giving a ratio of 9/5 = 1.8), then shifting the result by 32 to account for the different zero points (water freezes at 0°C but 32°F).
Worked Example
Convert 100°C (the boiling point of water at sea level) to Fahrenheit:
- Multiply by 9/5: 100 × 9/5 = 100 × 1.8 = 180
- Add 32: 180 + 32 = 212°F
So 100°C = 212°F. This is one of the most useful reference points to memorise.
How to Convert Fahrenheit to Celsius
The reverse formula is:
C = (F - 32) × 5/9
For example, to convert 98.6°F (normal body temperature) to Celsius:
- Subtract 32: 98.6 - 32 = 66.6
- Multiply by 5/9: 66.6 × 5/9 = 66.6 × 0.5556 = 37°C
Quick Mental Estimate
For a rough Celsius to Fahrenheit estimate in your head, double the Celsius temperature and add 30. For example, 20°C gives approximately 20 × 2 + 30 = 70°F (the exact answer is 68°F). This is slightly off but useful when precision is not needed.
In the other direction, subtract 30 from Fahrenheit and divide by 2 to estimate Celsius. For example, 80°F gives approximately (80 - 30) / 2 = 25°C (the exact answer is 26.7°C).
The Celsius and Fahrenheit Scales
The Celsius scale (formerly called centigrade) was developed in the 18th century and is defined so that water freezes at 0°C and boils at 100°C at standard atmospheric pressure. It is the scale used in most countries worldwide and in all scientific work.
The Fahrenheit scale was developed by Daniel Gabriel Fahrenheit in the early 1700s. It sets the freezing point of water at 32°F and the boiling point at 212°F. It is still used in everyday life in the United States and a small number of other countries. New Zealand uses Celsius for all official and everyday temperature measurements.
The Kelvin scale is the SI (metric) absolute temperature scale. Zero Kelvin (absolute zero) is the coldest possible temperature, equal to -273.15°C or -459.67°F. Kelvin values are used in scientific calculations such as gas laws and thermodynamics. To convert Celsius to Kelvin, add 273.15.
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Sources and method: International Bureau of Weights and Measures (BIPM), SI Brochure, 9th edition (2019). The Celsius to Fahrenheit formula F = (C × 9/5) + 32 is standardised by international agreement. The Kelvin scale offset of 273.15 is defined in the 2019 revision of the SI.
This converter applies the standard, exact Celsius to Fahrenheit conversion formula. Boiling and freezing points quoted are at standard atmospheric pressure (101.325 kPa). Actual boiling point varies slightly with altitude and atmospheric conditions.