Conversor de temperatura
Converta instantaneamente entre Celsius, Fahrenheit, Kelvin e Rankine, com o cálculo passo a passo e uma tabela de referência de temperaturas importantes.
Como usar esta calculadora
- 1Enter the temperature you have.
- 2Choose the scale it is in and the scale you want.
- 3All four scales are shown at once, so you never need a second conversion.
Como funciona
Fórmulas de conversão de temperatura
°F = °C × 9/5 + 32 °C = (°F − 32) × 5/9 K = °C + 273,15 °R = °F + 459,67 °C = K − 273,15
Converter temperaturas exige ajustar duas coisas: o ponto zero de cada escala e o tamanho dos seus graus. Celsius e Kelvin compartilham o tamanho do grau, mas diferem no zero (273,15); Fahrenheit e Rankine fazem o mesmo entre si. Por isso, passar de Celsius para Fahrenheit não é só multiplicar: é preciso escalar por 9/5 e depois deslocar o zero somando 32.
Exemplo resolvido
20 °C equivalem a 20 × 9/5 + 32 = 68 °F, ou a 20 + 273,15 = 293,15 K. Ao contrário, 98,6 °F são (98,6 − 32) × 5/9 = 37 °C, a temperatura corporal normal.
Conversor de temperatura: o guia completo
The mental shortcut for Celsius and Fahrenheit
The exact conversion is × 1.8 + 32, which is awkward in your head. The usual approximation — double it and add 30 — is accurate to within a couple of degrees across normal weather temperatures. 20 °C becomes 70 °F by the shortcut and 68 °F exactly; 30 °C becomes 90 °F by the shortcut and 86 °F exactly.
A few anchor points are worth memorising outright: 0 °C is 32 °F, 10 °C is 50 °F, 20 °C is 68 °F, 30 °C is 86 °F, and 37 °C is 98.6 °F. Everything between can be interpolated well enough for practical purposes.
−40 is the one point where the two scales agree exactly. It is the only such point, because the two lines have different slopes and can only cross once.
Why Kelvin has no degree sign
Kelvin is an absolute scale: its zero is absolute zero, the temperature at which all classical thermal motion stops. Because there is no arbitrary offset, kelvin values are proportional — 200 K really is twice as hot as 100 K in a way that 200 °C is not twice 100 °C.
That is why the SI unit is written as "300 K", not "300 °K". The degree symbol marks a scale with an arbitrary zero, and kelvin does not have one. All the gas laws, blackbody radiation, and thermodynamic equations require kelvin for exactly this reason.
Rankine is the same idea applied to Fahrenheit degrees: absolute zero is 0 °R, and water freezes at 491.67 °R. It survives in some American engineering fields, particularly aerospace and HVAC.
Converting a difference is not converting a value
This trips up thermostat specifications, engineering tolerances, and weather reports alike. A temperature of 5 °C is 41 °F. But a temperature difference of 5 °C is a difference of 9 °F — you multiply by 1.8 and skip the offset entirely.
The rule: use the full formula for a point on the scale, and only the ratio for an interval. Since a kelvin and a Celsius degree are the same size, a temperature difference in °C and in K is numerically identical, which is why heat-transfer equations quote units as W/(m·K) without ambiguity.
Perguntas frequentes
Como converter de Celsius para Fahrenheit?
Multiplique os graus Celsius por 9/5 (ou 1,8) e some 32. Por exemplo, 20 °C × 1,8 + 32 = 68 °F. Para o caminho inverso, subtraia 32 e multiplique por 5/9.
O que é o zero absoluto?
É a temperatura mais baixa possível: 0 K, equivalente a −273,15 °C ou −459,67 °F. Nesse ponto cessa o movimento térmico das partículas. As escalas Kelvin e Rankine partem daí, por isso nunca têm valores negativos.
Por que a conversão não é uma simples multiplicação?
Porque as escalas não compartilham o mesmo ponto zero. Converter um valor de temperatura envolve escalar e depois deslocar o zero, enquanto converter uma diferença exige apenas escalar. Por isso 1 °C de diferença são 1,8 °F, mas o valor 1 °C equivale a 33,8 °F.