Temperature Converter Widget

Add a temperature converter to your science, cooking or weather page. Enter a temperature in any of four scales and see the other three at once, with the conversion formulas written out underneath.

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<iframe src="https://a2z.tools/embed/w/temperature-converter" title="Temperature Converter by A2Z Tools" width="100%" height="390" style="border:0;width:100%" loading="lazy" allow="clipboard-write"></iframe>

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How it works

The widget converts the input to kelvin and then to every other scale using the exact defining relations - no rounded constants - so -40 degrees Celsius and -40 degrees Fahrenheit agree exactly. Values below absolute zero (0 K) are physically impossible and are refused with an explanation. Results show up to four decimal places.

Method

  • F = C x 9/5 + 32; C = (F - 32) x 5/9
  • K = C + 273.15; R = K x 9/5 = F + 459.67
  • Absolute zero: 0 K = -273.15 C = -459.67 F = 0 R

Worked examples

Boiling water

Inputs: 100 C

Result: 212 F, 373.15 K, 671.67 R

100 x 9/5 + 32 = 212; 373.15 x 9/5 = 671.67.

The crossover point

Inputs: -40 F

Result: -40 C, 233.15 K, 419.67 R

(-40 - 32) x 5/9 = -40.

A familiar body temperature

Inputs: 98.6 F

Result: 37 C, 310.15 K, 558.27 R

(98.6 - 32) x 5/9 = 37 exactly; 98.6 F is the conventional reference, not a medical threshold.

Limitations

  • Temperature differences are not converted separately: a rise of 10 C is a rise of 18 F, not 50 F - use the formulas without the offset for intervals.
  • Historic scales such as Reaumur, Delisle, Newton and Romer are not included.
  • Four decimal places at most, so a value like 1/3 of a degree is shown rounded.

Where publishers use it

  • School science pages on heat and the Kelvin scale
  • Recipe sites that publish oven temperatures for international readers
  • Weather and travel blogs comparing climates
  • Engineering references that still use Rankine

Questions

At what temperature are Celsius and Fahrenheit equal?

At -40: -40 C is exactly -40 F.

Why can't I enter -300 C?

It is below absolute zero, -273.15 C, the lowest temperature possible, so it cannot be converted to kelvin.

What is the Rankine scale?

An absolute scale with Fahrenheit-sized degrees: 0 R is absolute zero and water freezes at 491.67 R. It is still used in some US engineering work.

Does it round?

Results show up to four decimal places; the conversion itself uses exact constants.

What oven setting is 180 C?

356 F. Recipes usually round it to 350 F (about 177 C), since oven dials move in 25-degree steps and thermostats vary by more than that.

Sources

  1. The International System of Units (SI Brochure), definition of the kelvin and the degree Celsius - BIPM . t/degC = T/K - 273.15
  2. NIST Special Publication 811, sections 4.2.1.1 and B.9 (temperature) - NIST . Fahrenheit and Rankine relations: T/K = (t/degF + 459.67) / 1.8; T/K = (T/degR) / 1.8

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A2Z Tools Temperature Converter
https://a2z.tools/embed/temperature-converter

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