Temperature converter
Convert any temperature via the SI Kelvin. Exact textbook / ITS-90 relations — see the arithmetic for your input, plus a table of all five scales (°C, °F, K, °R, °Ré) with common temperatures: body temperature, freezing and boiling water, oven settings.
Defaults to your region. Switch to compare any other scale.
Canonical path is Kelvin (SI). Celsius offset 273.15; Fahrenheit via 5/9; Rankine = K × 9/5.
Result
20 °C
°F → °C
(68 − 32) × 5/9 + 273.15 = 293.15 K; 293.15 − 273.15 = 20 °C
- In SI Kelvin293.15 K
- Formula (from)T_K = (T_F − 32) × 5/9 + 273.15
- Formula (to)T_C = T_K − 273.15
- How calculated(68 − 32) × 5/9 + 273.15 = 293.15 K; 293.15 − 273.15 = 20 °C
- Cross rate1 °F → −17.2222 °C
Via Kelvin (SI)
Standards: BIPM SI + ITS-90. Absolute zero = 0 K = −273.15 °C. (68 − 32) × 5/9 + 273.15 = 293.15 K; 293.15 − 273.15 = 20 °C
Your value and common temperatures in every scale
| Reference point | °C | °F | K | °R | °Ré |
|---|---|---|---|---|---|
| Your value: 68 °F | 20 | 68 | 293.15 | 527.67 | 16 |
| Absolute zero | −273.15 | −459.67 | 0 | 0 | −218.52 |
| −40°: Celsius equals Fahrenheit | −40 | −40 | 233.15 | 419.67 | −32 |
| Water freezes | 0 | 32 | 273.15 | 491.67 | 0 |
| Room temperature | 20 | 68 | 293.15 | 527.67 | 16 |
| Normal body temperature | 37 | 98.6 | 310.15 | 558.27 | 29.6 |
| Fever threshold | 38 | 100.4 | 311.15 | 560.07 | 30.4 |
| Water boils (sea level) | 100 | 212 | 373.15 | 671.67 | 80 |
| Oven: low (300 °F) | 148.89 | 300 | 422.04 | 759.67 | 119.11 |
| Oven: moderate (350 °F) | 176.67 | 350 | 449.82 | 809.67 | 141.33 |
| Oven: hot (400 °F) | 204.44 | 400 | 477.59 | 859.67 | 163.56 |
| Oven: very hot (450 °F) | 232.22 | 450 | 505.37 | 909.67 | 185.78 |
About this tool
Temperature conversion goes through Kelvin, the SI base unit. From Celsius: T_K = T_C + 273.15. From Fahrenheit: first T_C = (T_F − 32) × 5/9, then add 273.15. Rankine is an absolute scale like Kelvin but with Fahrenheit-sized degrees: T_R = T_K × 9/5.
Absolute zero is 0 K = −273.15 °C = −459.67 °F = 0 °R. Values below absolute zero are physically impossible; this tool still shows the arithmetic for learning.
Use the all-scales table for weather, cooking, science homework, or engineering. Pair with the length and weight converters for other unit work.
Formula
T_K = T_C + 273.15T_C = (T_F − 32) × 5/9T_F = T_C × 9/5 + 32T_R = T_K × 9/5 = T_F + 459.67T_Ré = T_C × 4/5T_K = T_Ré × 5/4 + 273.15
How it is calculated
- Enter a temperature and pick the From and To scales — the result updates as you type.
- The value is converted to Kelvin (SI) first, e.g. T_K = T_C + 273.15.
- Kelvin is converted to the target scale, e.g. T_F = (T_K − 273.15) × 9/5 + 32.
- Read the rows for the exact arithmetic of your input.
- Use the table to see your value in °C, °F, K, °R and °Ré next to common temperatures such as body temperature, boiling water and oven settings.
Questions
How does temperature conversion work?
All temperatures go through Kelvin: convert the source to K, then from K to the target. Example: 20 °C → 20 + 273.15 = 293.15 K → (293.15 − 273.15) × 9/5 + 32 = 68 °F.
What is absolute zero?
Absolute zero is 0 K = −273.15 °C = −459.67 °F = 0 °R — the lowest thermodynamic temperature. Kelvin and Rankine start there; Celsius and Fahrenheit use fixed offsets.
Celsius vs Kelvin vs Rankine?
Celsius and Kelvin share the same degree size (1 °C = 1 K). Rankine uses Fahrenheit-sized degrees on an absolute scale (1 °R = 1 °F). T_R = T_K × 9/5.
What is normal body temperature in Fahrenheit?
About 37 °C = 98.6 °F (310.15 K). Normal readings range roughly from 36.1 to 37.2 °C (97 to 99 °F); 38 °C (100.4 °F) or more is usually treated as a fever.
What is 350 °F in Celsius?
(350 − 32) × 5/9 = 176.67 °C. Recipes usually round it to 175 or 180 °C (gas mark 4). Likewise 400 °F = 204.4 °C ≈ 200 °C and 425 °F = 218.3 °C ≈ 220 °C. For a fan oven many recipes lower the setting by about 20 °C.
What is the Réaumur scale?
A historical scale on which water freezes at 0 °Ré and boils at 80 °Ré, so 1 °Ré = 1.25 °C: T_C = T_Ré × 5/4 and T_Ré = T_C × 4/5. It was common in parts of Europe in the 18th and 19th centuries and still turns up in old recipes and in cheese and sugar making.
Are the results official metrology advice?
No. Calculate This is educational. For legal metrology or calibrated instruments, follow your national institute (e.g. NIST, BIPM) and ITS-90 guidance.