Temperature Converter

Real-World Temperature Reference Points

Landmark	°C	°F	K	°R
Absolute Zero	−273.15	−459.67	0	0
Dry Ice (CO₂)	−78.5	−109.3	194.65	350.37
Water Freezes	0	32	273.15	491.67
Room Temperature	20–22	68–72	293–295	527–531
Human Body Temp	37	98.6	310.15	558.27
Oven — 350°F (Baking)	176.7	350	449.85	809.67
Water Boils (sea level)	100	212	373.15	671.67
Surface of the Sun	5,505	9,941	5,778	10,400

Temperature Conversion Formulas

From	To	Formula
°C	°F	°F = (°C × 9/5) + 32
°C	K	K = °C + 273.15
°C	°R	°R = (°C + 273.15) × 9/5
°F	°C	°C = (°F − 32) × 5/9
°F	K	K = (°F + 459.67) × 5/9
°F	°R	°R = °F + 459.67
K	°C	°C = K − 273.15
K	°F	°F = (K × 9/5) − 459.67
K	°R	°R = K × 9/5
°R	°C	°C = (°R × 5/9) − 273.15
°R	°F	°F = °R − 459.67
°R	K	K = °R × 5/9

Which Temperature Scale Is Used Where?

°C

Celsius

The global standard for everyday use. Used in weather forecasts, cooking, medicine, and science in most countries. Water freezes at 0°C and boils at 100°C.

°F

Fahrenheit

Primarily used in the United States for weather, cooking, and body temperature. Water freezes at 32°F and boils at 212°F. Still common in US medicine and aviation.

K

Kelvin

The SI base unit for temperature. Used in science, physics, and astronomy. Starts at absolute zero (0 K) — no negative values exist. Same degree size as Celsius.

°R

Rankine

An absolute scale like Kelvin but using Fahrenheit-sized degrees. Used in US thermodynamics, aerospace engineering, and HVAC calculations. 0°R = absolute zero.

Quick Mental Math Shortcuts

Rough °C → °F (Good for weather)

Double the Celsius value and add 30. This is an approximation — accurate enough for everyday weather temperatures, though it drifts at extremes.

Example: 20°C → (20 × 2) + 30 = 70°F (actual: 68°F)

Precise °C → °F (Multiply then add)

Multiply the Celsius value by 1.8, then add 32. Easier to think of than 9/5 — the math is the same.

Example: 100°C → (100 × 1.8) + 32 = 212°F

°C → K (Just add 273)

Kelvin = Celsius + 273.15. For quick estimates, just add 273. The degree size is identical — only the zero point differs.

Example: 25°C → 25 + 273 = 298 K (actual: 298.15 K)

Body Temp anchor point

Remember: 37°C = 98.6°F. This is the most commonly needed medical conversion — memorize it and you can estimate nearby values quickly.

38°C (mild fever) ≈ 100.4°F | 39°C (high fever) ≈ 102.2°F

How to Use the Temperature Converter

Enter a Temperature Value

Type any number into the input field. Decimals are supported (e.g. 98.6). Negative numbers work for Celsius and Fahrenheit. You cannot enter a value below absolute zero in Kelvin or Rankine.

Select Your Starting Scale

Use the "Convert From" dropdown to select the scale your value is in — Celsius, Fahrenheit, Kelvin, or Rankine.

Click Convert

Press the Convert button to see all four results at once. Each result card shows the converted value and its unit symbol.

Copy Results or Explore the Formulas

Use the Copy button on any result card to copy that value to your clipboard. Click Show Formula on any card to see the step-by-step conversion math for students and engineers.

Frequently Asked Questions

What is the formula to convert Celsius to Fahrenheit?

Multiply the Celsius value by 9/5 (or 1.8) then add 32: °F = (°C × 9/5) + 32. For example, 100°C = (100 × 1.8) + 32 = 212°F. To go the other way: °C = (°F − 32) × 5/9.

What is the difference between Kelvin and Celsius?

Kelvin and Celsius have the same degree size — a 1°C change equals a 1 K change. The only difference is the zero point. Celsius sets 0 at the freezing point of water, while Kelvin starts at absolute zero (the coldest possible temperature). To convert: K = °C + 273.15.

What is Rankine and who uses it?

Rankine is an absolute temperature scale like Kelvin, but uses Fahrenheit-sized degrees instead of Celsius-sized degrees. Absolute zero is 0 °R, and water freezes at 491.67 °R. It is primarily used in US engineering disciplines — particularly thermodynamics, aerospace, and HVAC — where the Fahrenheit system is standard but an absolute scale is required.

Can I convert negative temperatures?

Yes — negative values are valid in Celsius and Fahrenheit. However, Kelvin and Rankine cannot go below zero because they start at absolute zero. If you enter a value that would produce a negative Kelvin or Rankine result, the tool will display a warning instead of an invalid result.

What is absolute zero in all four temperature scales?

Absolute zero is the lowest possible temperature — the point at which all molecular motion theoretically stops. In each scale: 0 K | 0 °R | −273.15°C | −459.67°F. It has never been achieved in practice, though scientists have gotten within billionths of a degree of it.

Visual Temperature Scale