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Fahrenheit to Kelvin Converter

Convert Fahrenheit to kelvins or kelvins to Fahrenheit, going through Celsius with every step shown. Readings below absolute zero aren't allowed.

Level: Grades 6–7

  • Common Core standard 6.EE.A.2.cEvaluate expressions at specific values of their variables. Include expressions that arise from formulas used in real-world problems. Perform arithmetic operations, including those involving whole-number exponents, in the conventional order when there are no parentheses to specify a particular order (Order of Operations).
Printable worksheet

Fahrenheit to Kelvin Converter

Know the answer you need? Pick an input to work backward.

Inputs

In °F when converting °F → K, or K for the reverse.

Direction

Result

In Kelvin

294.2611 K

70 °F = 294.261111 K

See the step-by-step solution ↓

Quick reference: °F to K
Quick reference: °F to K
Fahrenheit (°F)Kelvin (K)
-459.670
-40233.15
0255.37
32273.15
50283.15
68293.15
70294.26
77298.15
98.6310.15
100310.93
212373.15
350449.82
451505.93

Step-by-step solution

  1. Convert to Celsius: subtract 32, then multiply by 5/9

    (70 °F−32)×59=21.1111111111 °C

  2. Convert to Kelvin: add 273.15 to the Celsius value

    21.1111111111 °C+273.15=294.2611111111 K

Test yourself

20 quick questions built from this calculator's formula: work out results, predict what happens when an input changes, and work backward from an answer. Every answer comes with the working.

What this calculator does

Turn a Fahrenheit temperature into kelvins, or kelvins back into Fahrenheit. Fahrenheit is the everyday US scale. Kelvin is the scientific scale that starts at absolute zero, the coldest anything can get.

You'll need this when US engineering or weather data has to go into a physics formula. It also comes up in student problems that mix unit systems. It also helps when you read a kelvin value and want a familiar feel for it. Examples are a light bulb's color temperature or a spec for something super-cold (cryogenic).

Fahrenheit and kelvin differ in both the size of a degree and where zero sits. So the conversion has two parts. The clearest route goes through Celsius. Take away the 32-degree offset and multiply by 5/9 to reach Celsius, then add 273.15. The working below the result shows each part with your numbers.

Where it's used

Why this math matters outside the classroom:

  • Room temperature. A 68 °F room is (68 − 32) × 5 ÷ 9 + 273.15 = 293.15 K.
  • Gas law homework. US chemistry students convert a 77 °F lab temperature to 298.15 K before using PV = nRT.
  • Equipment ratings. Engineers converting a 140 °F equipment rating get 333.15 K.
  • Absolute zero. Absolute zero, 0 K, is −459.67 °F on the Fahrenheit scale.
  • Climate data. Climate datasets stored in kelvins turn 300 K into about 80.3 °F for a US audience.

Grade level and standards: Grades 6–7; Common Core State Standards for Mathematics 6.EE.A.2.c. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.

How to use it

  1. Enter the temperature in °F or K.
  2. Choose Fahrenheit to Kelvin or Kelvin to Fahrenheit.
  3. Read the result and the two-step working. If you enter a value below absolute zero, you'll get an explanation instead of a number.

What the inputs mean

Temperature
A reading in °F (no lower than −459.67) for °F → K, or in kelvins (no lower than 0) for K → °F.
Direction
Choose the scale of the number you're entering.

Formula and method

K = (°F − 32) × 5/9 + 273.15
°F = (K − 273.15) × 9/5 + 32
K = (°F + 459.67) × 5/9

In these formulas, K is the temperature in kelvins and °F is the temperature in degrees Fahrenheit. A kelvin is the same size as a Celsius degree, which is 9/5 of a Fahrenheit degree. So to turn a Fahrenheit difference into a kelvin difference, multiply it by 5/9.

The third form first shifts Fahrenheit up to the Rankine scale. Rankine uses Fahrenheit-sized degrees but starts at absolute zero. Then it multiplies by 5/9. It gives exactly the same answer as the two-step route through Celsius shown in the working.

Worked example

Room temperature is 70 °F. What is it in kelvins?

  1. Subtract 32 and multiply by 5/9: (70 − 32) × 5/9 = 21.1111… °C.
  2. Add 273.15: 21.1111… + 273.15 = 294.2611… K.

Result: 70 °F is about 294.26 K.

Understanding the result

Here's a quick mental shortcut. Add 460 to the Fahrenheit reading and multiply by 5/9 (a little over half). For 70 °F: 530 × 5/9 ≈ 294.4 K. That's about 0.2 K above the exact 294.26 K, because 460 rounds up the true 459.67.

Reference points: −459.67 °F = 0 K (absolute zero); −40 °F = 233.15 K; 0 °F ≈ 255.37 K; 32 °F = 273.15 K; 68 °F = 293.15 K; 212 °F = 373.15 K, water's boiling point at sea level.

Color temperature on bulbs (for example 2,700 K warm white) is always given in kelvins. You can convert it to Fahrenheit, but the result means nothing useful for lighting.

Assumptions and limitations

  • Inputs are temperature readings, not temperature differences.
  • For a temperature difference, multiply the °F change by 5/9 to get kelvins. Don't apply the offsets.
  • Readings below absolute zero are rejected.

Frequently asked questions

What is absolute zero in Fahrenheit?

−459.67 °F, which is 0 K and −273.15 °C.

Why not convert directly without Celsius?

You can: K = (°F + 459.67) × 5/9. It's the same formula, rearranged. The working goes through Celsius because most people already know the Celsius-to-kelvin step.

Is a change of 1 °F the same as a change of 1 K?

No. A 1 °F change is 5/9 K, about 0.556 K. A 1 K change is 1.8 °F.

How this calculator is checked

Method: Scale definitions: °C = (°F − 32) × 5/9 and K = °C + 273.15, both exact. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.

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