Toolvantas

Unit converter

Temperature Converter

Use this free temperature converter to convert between Celsius (°C), Fahrenheit (°F), Kelvin (K), Rankine (°R), Réaumur, and Delisle with worked formulas.

Convert temperature

Enter any temperature at or above absolute zero (0 K / −273.15 °C / −459.67 °F).

Negative and decimal temperatures are supported.
Adjust display rounding.

Reference benchmarks

Converted temperature

25 Celsius (°C) equals

77 °F
Thermodynamic Kelvin298.15 K
Physical reference contextWarm room temperature
Interval change (ΔT) in targetΔ25 °C = Δ45 °F
Above absolute zero+298.15 K

All temperature scales

    Worked calculation: (25 °C × 9/5) + 32 = 77 °F

    Core temperature conversion formulas

    Unlike length or weight, temperature scales have different zero points as well as different degree sizes, so conversions combine multiplication with an offset:

    • Celsius to Fahrenheit: °F = (°C × 9/5) + 32 (or °C × 1.8 + 32).
    • Fahrenheit to Celsius: °C = (°F − 32) × 5/9.
    • Celsius to Kelvin: K = °C + 273.15 (note: Kelvin uses K without a degree symbol).
    • Fahrenheit to Rankine: °R = °F + 459.67.
    • Celsius to Réaumur: °Ré = °C × 4/5.

    Point temperature vs. temperature interval (ΔT)

    • Reading a thermometer (point temperature): 10 °C on a weather forecast equals 50 °F because you add the 32-degree offset.
    • Measuring a temperature change (ΔT): If a room warms up by 10 °C, it warms up by 18 °F (not 50 °F!), because only the 9/5 scale ratio applies to differences. Check the Interval change (ΔT) tile whenever converting heating/cooling deltas.
    • Equal crossover point: Celsius and Fahrenheit read the exact same numerical value at −40 °C = −40 °F.

    Frequently asked questions

    How do I quickly estimate Celsius to Fahrenheit in my head?

    Double the Celsius temperature and add 30 for a fast weather estimate (for example, 20 °C × 2 + 30 = 70 °F; exact is 68 °F). For exact results, multiply by 1.8 and add 32.

    At what temperature are Celsius and Fahrenheit equal?

    They meet at −40 degrees: (−40 × 9/5) + 32 = −72 + 32 = −40. Both −40 °C and −40 °F represent the exact same temperature.

    Why can't I enter a temperature below −273.15 °C or 0 K?

    0 Kelvin (−273.15 °C or −459.67 °F) is thermodynamic absolute zero, the fundamental physical lower limit at which classical thermal motion ceases.

    Why is Kelvin written without a degree (°) symbol?

    Since 1967, the International System of Units (SI) defines the kelvin (symbol K) as an absolute base unit rather than a relative degree scale, whereas Celsius (°C) and Fahrenheit (°F) retain the degree symbol.

    What is the Rankine scale used for?

    Rankine (°R) is an absolute thermodynamic scale like Kelvin, starting at 0 °R = absolute zero, but using Fahrenheit-sized degree increments (1 K = 1.8 °R). It appears in aerospace and US thermodynamic engineering.

    How do oven temperatures convert between Celsius and Fahrenheit?

    A standard baking temperature of 180 °C equals 356 °F (commonly rounded to 350 °F in US recipes), while 200 °C equals 392 °F (often rounded to 400 °F). Fan/convection ovens typically run 15–20 °C cooler than conventional recipes.

    More on Toolvantas

    Related tools you may need

    Browse all tools →