Temperature Converter
Temperature Converter
Temperature Conversion Formulas
Unlike other unit conversions, temperature requires formulas with offsets — you cannot simply multiply by a factor.
Celsius ↔ Fahrenheit
| °C → °F | °F = °C × 9/5 + 32 |
| °F → °C | °C = (°F − 32) × 5/9 |
Quick trick: °C × 2 + 30 ≈ °F (within ±2° for 0–35°C range)
Celsius ↔ Kelvin
| °C → K | K = °C + 273.15 | exact |
| K → °C | °C = K − 273.15 | exact |
Fahrenheit ↔ Kelvin
| °F → K | K = (°F − 32) × 5/9 + 273.15 |
| K → °F | °F = (K − 273.15) × 9/5 + 32 |
Rankine & Réaumur formulas
Rankine
| °F → °R | °R = °F + 459.67 | exact |
| °C → °R | °R = (°C + 273.15) × 9/5 | |
| K → °R | °R = K × 9/5 | exact |
Réaumur
| °C → °Ré | °Ré = °C × 4/5 | exact |
| °Ré → °C | °C = °Ré × 5/4 | exact |
The offset 273.15 between Celsius and Kelvin is exact by definition (13th CGPM, 1967). The ratio 9/5 between Fahrenheit and Celsius degree sizes is also exact. −40 is the only temperature where Fahrenheit and Celsius are equal: −40°C = −40°F.
Temperature Reference Points
Key temperatures across all scales — useful for quick verification and everyday reference.
| Reference | °C | °F | K | Context |
|---|---|---|---|---|
| Absolute zero | −273.15 | −459.67 | 0 | Lowest possible temperature |
| −40 crossover | −40 | −40 | 233.15 | °C = °F at this point |
| Freezing point of water | 0 | 32 | 273.15 | At 1 atm pressure |
| Room temperature | 20–22 | 68–72 | 293–295 | Comfortable indoor |
| Normal body temperature | 37 | 98.6 | 310.15 | Human average (oral) |
| Fever threshold | 38 | 100.4 | 311.15 | Medical reference |
| Boiling point of water | 100 | 212 | 373.15 | At 1 atm pressure |
| Oven — moderate | 180 | 350 | 453.15 | Baking, Gas Mark 4 |
Freezing and boiling points of water are at standard pressure (1 atm = 101,325 Pa). At higher altitudes, water boils below 100°C. Normal body temperature varies between 36.1–37.2°C (97–99°F); the classic "98.6°F" comes from Carl Wunderlich's 1868 study.
About Temperature Scales
Weather & Daily Life
Most countries use Celsius (°C). The US uses Fahrenheit (°F). Quick reference: 0°C = freezing, 20°C = comfortable, 30°C = hot, 40°C = extreme heat. Equivalent in °F: 32°F, 68°F, 86°F, 104°F.
Medical
Body temperature is measured in °C (most countries) or °F (US). Normal: 36.1–37.2°C (97–99°F). Fever: above 38°C (100.4°F). Hypothermia: below 35°C (95°F).
Cooking & Baking
Oven temperatures use °C (metric), °F (US/UK), or Gas Mark (UK). Key points: 180°C = 350°F (moderate oven), 200°C = 400°F (hot oven), 220°C = 425°F (very hot). See our Gas Mark converter.
Science & Engineering
The kelvin (K) is the SI base unit of thermodynamic temperature, redefined in 2019 via the Boltzmann constant. Kelvin uses the same degree size as Celsius but starts at absolute zero. Rankine (°R) is the Fahrenheit-based absolute scale, used in some US engineering contexts.
Unlike length or weight, temperature scales are not related by simple multiplication. Each scale has a different zero point (offset), which is why conversion formulas include addition/subtraction — not just a factor. This is unique among physical quantities.
Popular Temperature Conversions
Celsius & Fahrenheit
Kelvin Conversions
Conversion Charts & Tables
Printable charts and reference tables for temperature conversions:
Celsius Conversions
Fahrenheit Conversions
Kelvin Conversions
Frequently Asked Questions
What is the formula to convert Fahrenheit to Celsius?
Subtract 32 from the Fahrenheit value, then multiply by 5/9. For example, 72°F = (72 − 32) × 5/9 = 22.2°C. For quick mental math, subtract 30 and divide by 2.
What is normal body temperature in both scales?
The traditional normal body temperature is 98.6°F (37°C), established by Wunderlich in 1868. Modern studies suggest the actual average is closer to 97.9°F (36.6°C). A fever is generally defined as 100.4°F (38°C) or higher.
At what temperature are Fahrenheit and Celsius the same?
At −40 degrees — the only point where both scales give the same number. This can be proven by setting °F = °C in the conversion formula and solving.
Why does the US use Fahrenheit while most countries use Celsius?
Fahrenheit was widely adopted in English-speaking countries in the 18th century. Most countries later switched to Celsius as part of metrication. The US attempted metrication in the 1970s but the effort stalled, and Fahrenheit persists in everyday American life.
Cooking & Kitchen
- Cooking Converters — recipe-specific ingredient and volume tools
- Gas Mark Oven Temperatures — oven gas mark conversions for UK/EU recipes (free printable PDF + Pinterest chart)
- Body Temperature Chart — normal, fever and hypothermia ranges in °C and °F
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 |
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.
Related Converter Categories
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- Pressure Converter — Gas law: pressure × volume ∝ temperature
