What temperature is the same in Celsius and Fahrenheit?

-40 degrees is identical in both scales (-40 °C = -40 °F).

Why doesn't Kelvin use a degree symbol?

Kelvin is an absolute unit of measure on a thermodynamic scale, so it is written simply as K rather than °K.

Subtract 30 from Fahrenheit and divide by 2 for a quick approximation (e.g. 70 °F - 30 = 40; ÷ 2 ≈ 20 °C).

Enter any temperature value and select your starting scale to instantly convert between Celsius (°C), Fahrenheit (°F), Kelvin (K), and Rankine (°R).

Select your input temperature scale (Celsius, Fahrenheit, Kelvin, or Rankine).
Enter your numerical temperature value.
Read your instant converted values across all 4 temperature units simultaneously.

Temperature Conversion Equations

Fahrenheit = (°C × 9/5) + 32 · Kelvin = °C + 273.15 · °C = (°F − 32) × 5/9 · Rankine = (K) × 1.8

Absolute lower bound is -273.15 °C (0 Kelvin).

25 °C → Fahrenheit: (25 × 1.8) + 32 = 77 °F, Kelvin: 25 + 273.15 = 298.15 K, Rankine: 536.67 °R.

Celsius (°C) and Fahrenheit (°F) are relative scales, whereas Kelvin (K) and Rankine (°R) are absolute thermodynamic temperature scales.
Absolute Zero is 0 K = -273.15 °C = -459.67 °F = 0 °R — the theoretical point where all molecular motion ceases.
Water freezes at 0 °C (32 °F, 273.15 K) and boils at 100 °C (212 °F, 373.15 K) under standard atmospheric pressure.
Conversion shortcut: 1 °C change equals a 1.8 °F change (e.g. going from 20 °C to 21 °C increases Fahrenheit from 68 °F to 69.8 °F).

Celsius and Fahrenheit base zero on freezing/weather points, whereas Kelvin starts at physical absolute zero without negative numbers.

Kelvin is the SI unit used in physics and astronomy; Rankine is the absolute imperial scale used in aerospace thermodynamics.

Body temperature: 37 °C / 98.6 °F. Room temperature: 20–22 °C / 68–71.6 °F.

What temperature is the same in Celsius and Fahrenheit?: -40 degrees is identical in both scales (-40 °C = -40 °F).
Why doesn't Kelvin use a degree symbol?: Kelvin is an absolute unit of measure on a thermodynamic scale, so it is written simply as K rather than °K.
How do I convert Fahrenheit to Celsius in my head?: Subtract 30 from Fahrenheit and divide by 2 for a quick approximation (e.g. 70 °F - 30 = 40; ÷ 2 ≈ 20 °C).

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