| Reference Point | Celsius (°C) | Fahrenheit (°F) | Kelvin (K) |
|---|---|---|---|
| Absolute Zero | −273.15 | −459.67 | 0 |
| Water Freezes | 0 | 32 | 273.15 |
| Room Temperature | 20–22 | 68–72 | 293–295 |
| Normal Body Temp | 37.0 | 98.6 | 310.15 |
| Fever Threshold | 38.0 | 100.4 | 311.15 |
| Water Boils (sea level) | 100 | 212 | 373.15 |
| Oven — Medium | 180 | 356 | 453.15 |
| Oven — High | 220 | 428 | 493.15 |
Temperature Conversion Guide — °C, °F, Kelvin & Rankine Explained
Temperature is the only unit conversion that uses addition and subtraction — not just multiplication — because the scales have different zero points. That is why you cannot just multiply to convert.
Celsius to Fahrenheit Formula
°F = (°C × 9/5) + 32
Example: 100°C → (100 × 1.8) + 32 = 212°F
Quick estimate: double the Celsius and add 30 (gives approximate answer for everyday temps).
Fahrenheit to Celsius Formula
°C = (°F − 32) × 5/9
Example: 98.6°F → (98.6 − 32) × 5/9 = 37°C
Quick estimate: subtract 30 and halve the result.
Kelvin Scale
K = °C + 273.15 | °C = K − 273.15
Kelvin is the SI base temperature unit. 0 K = absolute zero (theoretically the coldest possible temperature). Water freezes at 273.15 K, boils at 373.15 K. No degree symbol used with Kelvin.
Rankine Scale
°R = °F + 459.67 | °R = K × 9/5
Rankine is the Fahrenheit equivalent of Kelvin — absolute scale using Fahrenheit-sized degrees. Used in US engineering and thermodynamics.