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Temperature Unit Conversion

Convert temperature units between Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur. Fast and accurate temperature conversion for science, cooking, engineering, and weather applications. Supports absolute zero and triple point references.

Temperature Conversion Formulas

°F = (°C × 9/5) + 32 | °C = (°F - 32) × 5/9 | K = °C + 273.15 | °R = °C × 4/5

Variables:

  • °CCelsius
    Metric temperature scale (freezing point 0°C)(e.g.: 25°C (comfortable room))
    💡 Weather forecast, cooking
  • °FFahrenheit
    US temperature scale (freezing point 32°F)(e.g.: 77°F = 25°C)
    💡 US weather, oven (350°F), body temp 98.6°F
  • KKelvin
    SI unit (absolute zero 0 K)(e.g.: 298.15 K = 25°C)
    💡 Scientific physics, cryogenics, absolute temperature
  • °RReamur
    Rarely used scale (freezing point 0°R)(e.g.: 20°R = 25°C)
    💡 School physics problems, temperature history
  • TWater Freezing Point
    Phase transition point from liquid to solid(e.g.: 0°C = 32°F = 273.15 K)
    💡 Thermometer calibration, phase experiments
  • TWater Boiling Point
    Phase transition point from liquid to vapor(e.g.: 100°C = 212°F = 373.15 K)
    💡 Water heating, vapor pressure, cooking

Categories:

Below 0°CCold/freezing temperature
0°C - 30°CCool - comfortable temperature
30°C - 40°CHot - body temperature
Above 40°CVery hot temperature

How to Use KalkuLab Temperature Converter

KalkuLab Temperature Converter supports conversion between 4 temperature scales. Here's a complete usage guide:

  1. 1

    Enter Temperature Value

    Type the temperature value you want to convert in the input field. It can be positive, negative, or decimal numbers (e.g., 36.5 for body temperature).

  2. 2

    Select Source Unit

    Choose the temperature unit you are entering: Celsius (°C), Fahrenheit (°F), Kelvin (K), or Reamur (°R).

  3. 3

    Select Target Unit

    Choose the desired temperature unit for the conversion result. You can select more than one to see all conversions at once.

  4. 4

    Click Calculate

    Press the 'Calculate' button to get the complete conversion results along with calculation steps that clarify the process.

  5. 5

    Analyze Results

    Results will be displayed with 2 decimal precision. If you select all units, you will see conversions to all 4 scales at once for comparison.

💡 Tip:

  • •Celsius and Reamur share the same freezing point (0°), but different increments: 100°C = 80°R
  • •Fahrenheit is 'finer' for weather because 1°F ≈ 0.56°C, so changes appear smaller
  • •Absolute zero (0 K) = -273.15°C = -459.67°F, the lowest theoretically possible temperature
  • •Normal body temperature: 36.5-37.5°C = 97.7-99.5°F = 309.65-310.65 K
  • •Quick °C to °F estimate: multiply by 2 then add 30 (24°C ≈ 78°F, actual is 75.2°F)

Examples

Example 1: Office Room Temperature in Jakarta

Problem:

The AC in a Jakarta office is set to 23°C. What is this temperature in Fahrenheit and Kelvin if an American colleague asks?

Solution:
  1. 1.°F = (23 × 9/5) + 32 = 41.4 + 32 = 73.4°F
  2. 2.K = 23 + 273.15 = 296.15 K
  3. 3.°R = 23 × 4/5 = 18.4°R
Result:73.4°F, 296.15 K, 18.4°R

Room temperature 23°C is equivalent to 73.4°F (comfortable by US standards), 296.15 K (scientific scale), and 18.4°R. The American colleague will find it comfortable since 73°F is the ideal room temperature in the US.

Example 2: Cooking Chicken (US Recipe vs Indonesia)

Problem:

A US recipe calls for baking chicken at 350°F. What is this temperature in Celsius for an Indonesian electric oven?

Solution:
  1. 1.Use the formula: °C = (°F - 32) × 5/9
  2. 2.°C = (350 - 32) × 5/9 = 318 × 0.5556
  3. 3.°C = 176.67°C ≈ 177°C
Result:177°C

The oven should be set to 177°C to bake chicken according to the US recipe of 350°F. This is a high temperature (very hot oven) to ensure the chicken is cooked thoroughly.

Frequently Asked Questions

Why does Indonesia use Celsius and not Fahrenheit?
Indonesia adopted the metric system (SI) since independence, where Celsius is the standard temperature scale. Most countries in the world (except the US, Bahamas, and a few small countries) use Celsius because it is more intuitive: 0° water freezes, 100° water boils at 1 atm pressure.
What is absolute zero and why can't it be reached?
Absolute zero (0 K = -273.15°C) is the theoretical lowest temperature where particles stop moving completely and kinetic energy = 0. It cannot be fully reached because the third law of thermodynamics states that infinite cooling would be required. The coldest laboratory on Earth is approximately ± -273.144°C (0.006 K).
When do Celsius and Fahrenheit have the same value?
Celsius and Fahrenheit have the exact same value at -40 degrees: -40°C = -40°F. This is the only point where the two scales meet. Below -40°, Fahrenheit is 'colder' (lower number), above -40°, Celsius is 'hotter' (higher number).
Why is the Reamur scale rarely used nowadays?
The Reamur scale (0°R freezing point, 80°R boiling point) was created by René Antoine Ferchault de Réaumur in 1732. However, this scale lost popularity because Celsius is easier (100 degrees between freezing and boiling) and Fahrenheit is more precise for weather. Today Reamur only appears in physics history and school exercises.
How do I quickly convert Celsius to Fahrenheit without a calculator?
Estimating formula: Multiply Celsius by 2 then add 30. Example: 20°C ≈ (20×2)+30 = 70°F (actual is 68°F). To convert back: subtract 30 from Fahrenheit then divide by 2. Example: 80°F ≈ (80-30)/2 = 25°C (actual is 26.7°C). Accurate enough for quick estimates.

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References