Free Online Temperature Converter
🔒 Runs in your browser — nothing is sent to a serverTemperature converter for every common scale — Celsius (°C), Fahrenheit (°F), Kelvin (K) and Rankine (°R). Type a value on either side, pick the units, and the result updates instantly using the standard affine formulas. Useful for cooking, weather, fever readings, science homework and engineering thermodynamics. Everything runs 100% inside your browser; nothing is uploaded, logged or sent to any server.
Supported units: Celsius (°C), Fahrenheit (°F), Kelvin (K), Rankine (°R).
Celsius (°C) → Fahrenheit (°F)
Quick reference table
| Celsius (°C) | Fahrenheit (°F) |
|---|---|
| -40 °C | -40 °F |
| -20 °C | -4 °F |
| 0 °C | 32 °F |
| 10 °C | 50 °F |
| 20 °C | 68 °F |
| 25 °C | 77 °F |
| 37 °C | 98.6 °F |
| 40 °C | 104 °F |
| 60 °C | 140 °F |
| 100 °C | 212 °F |
How temperature scales relate (absolute zero, water phases)
All four scales describe the same physical quantity — average kinetic energy of particles — and are linked by simple affine transforms. Kelvin and Rankine are absolute scales: they start at absolute zero (0 K = 0 °R = −273.15 °C = −459.67 °F), the lowest temperature physically possible, where particle motion stops. Celsius and Fahrenheit are anchored to water phases at standard atmospheric pressure: water freezes at 0 °C / 32 °F / 273.15 K / 491.67 °R, and boils at 100 °C / 212 °F / 373.15 K / 671.67 °R. The Celsius and Kelvin steps are equal in size; the Fahrenheit and Rankine steps are equal in size; one Celsius step is 1.8 Fahrenheit steps.
Why Celsius and Fahrenheit have different zero points
Anders Celsius (1742) chose the freezing and boiling points of water as easily reproducible anchors and divided the interval into 100 degrees — a clean decimal scale that suited the metric system born in the same era. Daniel Fahrenheit (1724) had no such pure-water focus: he calibrated his thermometers against an ice-and-salt brine (the coldest temperature he could reliably reproduce) at 0 °F and against approximate human body temperature at 96 °F (later refined to 98.6 °F). The 32 °F freezing point and 212 °F boiling point are simply where water happened to land on his scale — not deliberate choices. The result is two equally valid systems with different numerical conventions, linked by F = C × 9/5 + 32.