Type a temperature into any scale and the other four update instantly. See the exact formula with your numbers, how it compares with freezing, body and boiling temperatures, and build a printable range table.
Last updated:
°C
°F
K
°R
°Ré
Reference points: freezing, boiling, body, oven (click to load)
Formula with your numbers
Temperature range table
From
To
20 rows. Click a row to load it into the converter.
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How to use the Temperature Converter
Type a temperature into any box: Celsius, Fahrenheit, Kelvin, Rankine or Réaumur.
Read the result: the other scales update instantly and the headline shows the most common pairing (°C ⇄ °F).
Check the working in “Formula with your numbers”, or click a reference point such as 37 °C or 350 °F.
Need a chart? Set the start and step of the range table and press Download CSV.
Temperature conversion formulas
Celsius and Kelvin share the same degree size; Fahrenheit and Rankine share a smaller one (1 °C = 1.8 °F). Réaumur divides the freezing-to-boiling interval into 80 steps instead of 100. Converting through Celsius keeps every formula simple:
Scale
From Celsius
To Celsius
Water freezes / boils
Fahrenheit (°F)
°F = °C × 9/5 + 32
°C = (°F − 32) × 5/9
32 / 212
Kelvin (K)
K = °C + 273.15
°C = K − 273.15
273.15 / 373.15
Rankine (°R)
°R = (°C + 273.15) × 9/5
°C = (°R − 491.67) × 5/9
491.67 / 671.67
Réaumur (°Ré)
°Ré = °C × 4/5
°C = °Ré × 5/4
0 / 80
Quick mental check for weather: double the Celsius value and add 30 to get a rough Fahrenheit figure (20 °C → about 70 °F; the exact answer is 68 °F). The shortcut drifts at extremes, so use the converter for cooking, lab or engineering work.
Reference temperatures in all five scales
Point
°C
°F
K
°R
°Ré
Absolute zero
−273.15
−459.67
0
0
−218.52
Lowest air temperature recorded on Earth (Vostok, 1983)
−89.2
−128.56
183.95
331.11
−71.36
Celsius and Fahrenheit meet
−40
−40
233.15
419.67
−32
Home freezer (0 °F is −17.8 °C)
−18
−0.4
255.15
459.27
−14.4
Water freezes (1 atm)
0
32
273.15
491.67
0
Refrigerator
4
39.2
277.15
498.87
3.2
Room temperature
20
68
293.15
527.67
16
Typical human body temperature
37
98.6
310.15
558.27
29.6
Highest air temperature recorded (Death Valley, 1913)
56.7
134.06
329.85
593.73
45.36
Water boils (1 atm)
100
212
373.15
671.67
80
Moderate oven (350 °F ≈ 177 °C)
180
356
453.15
815.67
144
Hot oven (450 °F)
232
449.6
505.15
909.27
185.6
Iron melts
1,538
2,800.4
1,811.15
3,260.07
1,230.4
Boiling and freezing points are for pure water at standard sea-level pressure (1 atm). Water boils at a lower temperature at altitude: roughly 95 °C (203 °F) in Denver.
Tips for accurate temperature conversions
Kelvin has no degree sign. Write 300 K, not 300 °K; the unit has been just “kelvin” since 1967.
Oven dials are rounded. Recipes convert 350 °F to 180 °C and 425 °F to 220 °C, even though the exact values are 176.7 °C and 218.3 °C.
Science uses absolute scales. Gas laws and radiation formulas need Kelvin (or Rankine), because doubling 10 °C does not double the energy, but doubling 283.15 K does.
Differences are not readings. A thermostat swing of 2 °C is 3.6 °F. Do not add 32 to a difference.
Frequently asked questions
What is the formula to convert Celsius to Fahrenheit?
Multiply by 9/5 (1.8) and add 32: °F = °C × 1.8 + 32. For example, 25 °C × 1.8 + 32 = 77 °F. To go back, subtract 32 and multiply by 5/9.
At what temperature are Celsius and Fahrenheit equal?
At −40. Setting °F = °C in °F = °C × 1.8 + 32 gives x = −40, so −40 °C is exactly −40 °F.
How do you convert Fahrenheit to Kelvin?
Use K = (°F − 32) × 5/9 + 273.15. For example, 68 °F is 20 °C, which is 293.15 K.
What is the Rankine scale?
Rankine is an absolute scale that uses Fahrenheit-sized degrees. 0 °R is absolute zero, and °R = °F + 459.67 = K × 1.8. It is still used in some US engineering thermodynamics.
What is the Réaumur scale?
An 18th-century scale that puts water freezing at 0 °Ré and boiling at 80 °Ré, so °Ré = °C × 0.8. It survives mainly in old European recipes and cheese-making texts.
Why does a temperature difference convert differently?
A change of 10 °C is a change of 18 °F, not 50 °F, because the +32 offset only applies to actual readings. Use the Δ panel in the converter for differences.
Can a temperature be below 0 K?
No. 0 K (−273.15 °C, −459.67 °F) is absolute zero, the lowest possible temperature, so the converter flags any value below it.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.