Temperature Converter - Celsius, Fahrenheit, Kelvin
Convert temperatures between Celsius, Fahrenheit, and Kelvin instantly as you type in any field. Free and browser-based, with the exact formulas and a reference table from absolute zero to oven heat.
21 C = 69.8 F = 294.15 K
Formulas
- F = C x 9/5 + 32
- C = (F - 32) x 5/9
- K = C + 273.15
| Reference point | C | F | K |
|---|---|---|---|
| Absolute zero | -273.15 | -459.67 | 0 |
| Coldest recorded on Earth (Vostok, 1983) | -89.2 | -128.56 | 183.95 |
| Home freezer | -18 | -0.4 | 255.15 |
| Water freezes | 0 | 32 | 273.15 |
| Cool spring day | 10 | 50 | 283.15 |
| Room temperature | 21 | 69.8 | 294.15 |
| Hot summer day | 35 | 95 | 308.15 |
| Human body temperature | 37 | 98.6 | 310.15 |
| Hottest recorded on Earth (Death Valley, 1913) | 56.7 | 134.06 | 329.85 |
| Water boils (at sea level) | 100 | 212 | 373.15 |
| Low oven (slow roasting) | 140 | 284 | 413.15 |
| Moderate oven (baking) | 180 | 356 | 453.15 |
| Hot oven (pizza, bread) | 230 | 446 | 503.15 |
Celsius, Fahrenheit, and Kelvin Explained
The Celsius scale, used by nearly every country in the world, pins 0 degrees to the freezing point of water and 100 degrees to its boiling point at sea level. Fahrenheit, still standard in the United States, puts those same two points at 32 and 212 degrees, which is why the conversion needs both a multiplication (9/5) and an offset (+32). Kelvin is the scientific scale: it uses the same step size as Celsius but starts at absolute zero, the temperature at which molecular motion reaches its minimum, so 0 K equals -273.15 C and nothing can be colder.
A few anchors make mental conversion easier. The scales cross at -40, the one temperature where Celsius and Fahrenheit agree. Room temperature is about 21 C or 70 F. Body temperature is 37 C or 98.6 F, and a fever above 38 C (100.4 F) is the common medical threshold. For a quick estimate from Celsius to Fahrenheit, double the number and add 30: it turns 20 C into an estimated 70 F versus the true 68 F, and stays within a couple of degrees for everyday weather.
Cooking is where most people meet the conversion in practice. American recipes bake at 350 F, which is 177 C, usually rounded to 180 C on European ovens. A hot 450 F oven for pizza or bread is about 230 C. Gas mark 4 equals 180 C or 350 F. If a recipe seems wildly off, check whether it assumes a fan (convection) oven: convention is to reduce a conventional-oven temperature by about 20 C (roughly 25-30 F) when using the fan.
The converter recalculates from whichever field you type in, flags anything below absolute zero as impossible, and rounds to two decimals. For related conversions, ToolForte also offers a general Unit Converter for length, weight, and volume, plus a Cooking Measurement Converter for cups, grams, and milliliters. Everything runs free in your browser.
How the Temperature Converter Works
- 01Type a temperature in any of the three fields: Celsius, Fahrenheit, or Kelvin.
- 02The other two fields convert instantly as you type.
- 03Check the formula box to see the exact math used.
- 04Use the reference table for anchors from absolute zero to a hot pizza oven.
Converting Between Celsius, Fahrenheit, and Kelvin
Celsius pins water's freezing point at 0 and boiling at 100; Fahrenheit puts the same points at 32 and 212, so converting requires multiplying by 9/5 and adding 32. Kelvin uses Celsius-sized degrees but starts at absolute zero (-273.15 C), the coldest temperature physically possible, so K = C + 273.15. The converter recalculates from whichever field you edit and flags any value below absolute zero as impossible.
When to Use This Tool
Use it for American recipes (350 F is 177 C, round to 180 C), weather reports when traveling, science homework that needs Kelvin, checking a fever reading from a Fahrenheit thermometer (100.4 F is the 38 C fever threshold), or setting a European oven for an American baking recipe. The reference table gives instant context without typing anything.
Common Use Cases
- Convert American recipe oven temperatures to Celsius Cooking Measurement Converter - Cups, Grams, ml, Spoons
- Understand Fahrenheit weather forecasts when traveling to the US
- Convert lab or homework values to Kelvin for physics and chemistry
Tips
- Quick estimate C to F: double it and add 30. Exact: multiply by 1.8 and add 32.
- Remember -40 is the same in both scales; it is a handy sanity check.
- A fever threshold to know: 38 C equals 100.4 F.
Frequently Asked Questions
- F = C x 9/5 + 32. So 20 C is 20 x 1.8 + 32 = 68 F. Going the other way, C = (F - 32) x 5/9, so 100 F is about 37.8 C. For a fast mental estimate, double the Celsius value and add 30.
- At -40 degrees. It is the single crossing point of the two scales: -40 C = -40 F. It falls out of the algebra when you set C equal to F in the conversion formula.
- Absolute zero is 0 K, equal to -273.15 C or -459.67 F. It is the temperature at which molecular thermal motion reaches its quantum minimum; nothing can be colder. That is why the converter rejects inputs below it.
- 350 F is 176.7 C, which European recipes round to 180 C. Other common oven marks: 325 F is about 165 C, 400 F is about 200 C, and 450 F is about 230 C. For fan (convection) ovens, reduce the conventional temperature by about 20 C.
- Because Kelvin is an absolute scale: 0 K means zero thermal energy, so ratios are meaningful (200 K really is twice as hot as 100 K in energy terms). Gas laws and thermodynamic equations only work with absolute temperatures, and Kelvin avoids negative numbers entirely.
What is the formula for Celsius to Fahrenheit?→
At what temperature are Celsius and Fahrenheit equal?→
What is absolute zero?→
What is 350 F in Celsius for baking?→
Why do scientists use Kelvin?→
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