Convert temperature between Celsius, Fahrenheit, Kelvin, Rankine, Réaumur, Delisle, Newton and Rømer — all eight scales at once with click-to-copy values.
Room temperature range.
Conversion formulas (from Celsius)
F = C × 9/5 + 32
K = C + 273.15
°R = (C + 273.15) × 9/5
°Ré = C × 4/5
°De = (100 − C) × 3/2
°N = C × 33/100
°Rø = C × 21/40 + 7.5
Reference points (click to load)
History
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Common C / F / K reference values
°C
°F
K
Note
-40
-40
233.15
C & F meet
0
32
273.15
Water freezes
20
68
293.15
Room
37
98.6
310.15
Body
100
212
373.15
Water boils
180
356
453.15
Oven bake
220
428
493.15
Oven roast
Frequently asked questions
Multiply the Celsius value by 9/5 (or 1.8) and add 32: F = C × 9/5 + 32. For example, 100 °C = 100 × 1.8 + 32 = 212 °F (water boiling). To go back, subtract 32 and divide by 1.8: C = (F − 32) / 1.8.
Absolute zero is the theoretical temperature at which molecular motion stops, defined as 0 K, −273.15 °C or −459.67 °F. Nothing can be colder. The Kelvin scale starts at absolute zero, which is why it has no negative values. The calculator prevents you from entering anything below this point in any scale.
Kelvin is the SI unit of temperature and is used in physics, chemistry, astronomy and engineering where absolute temperature matters — for thermodynamic formulas (PV = nRT), star colours, or calorimetry. For everyday weather, cooking or body temperature, Celsius or Fahrenheit are more convenient because they map to familiar landmarks (water freezing, room, body, boiling).
They are historical temperature scales. Réaumur (1730) sets water freezing at 0 and boiling at 80 — still occasionally seen in old European cheese, syrup and alcohol recipes. Newton (1701) used 0 at freezing and 33 at boiling. Rømer (1701) was the scale that inspired Fahrenheit. Delisle (1732) runs backwards: 0 at boiling, 150 at freezing. All are rarely used today but remain in textbooks and museums.
Many recipes use Fahrenheit (US), Celsius (EU, UK), or gas marks (UK, old recipes). A common rule: gas mark 1 ≈ 140 °C ≈ 275 °F, each step ≈ +14 °C / +25 °F. For conversions: 180 °C = 356 °F (moderate), 200 °C = 392 °F, 220 °C = 428 °F (roast). Round to the nearest standard setting on your oven.
At −40 degrees: −40 °C = −40 °F. This is the only point where the two scales cross. It happens because the slopes and offsets of C = (F − 32) / 1.8 intersect exactly at that value. Try entering −40 in any unit and check the grid.
Results are rounded for display. The calculator uses exact formulas; copy a value for full precision.
The Temperature Converter displays the same temperature in all eight historical and modern scales simultaneously: Celsius, Fahrenheit, Kelvin, Rankine, Réaumur, Delisle, Newton and Rømer. Pick the input scale, type a value, and every other scale updates instantly. Click any result to copy it to the clipboard. A visual thermometer shows where the temperature sits between −50°C and 250°C, with color bands from cold blue to oven red.nnExamples: enter 100 °C and read 212 °F, 373.15 K, 80 °Ré, 33 °N — water boiling. Enter 350 °F for baking and read 176.67 °C. Enter −40 to see Celsius and Fahrenheit meet. Absolute zero at −273.15 °C is enforced across every scale. Preset buttons cover water freezing, room, body temperature, boiling, and oven settings. Reference points list common landmarks and the FAQ explains historical scales and when to use Kelvin.