Temperature

1. Enter the temperature value you want to convert in the input field.
2. Select the scale of your input temperature: Celsius (°C), Fahrenheit (°F), or Kelvin (K).
3. The calculator instantly displays the equivalent temperatures in the other two scales.
4. Review the formula used and the step-by-step breakdown shown below the result.
5. Copy or note the converted values for your cooking, science, weather, or engineering use.

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

• °C — Temperature in degrees Celsius. Water freezes at 0 °C and boils at 100 °C at standard atmospheric pressure.
• °F — Temperature in degrees Fahrenheit. Water freezes at 32 °F and boils at 212 °F at standard atmospheric pressure.
• K — Temperature in Kelvin (no degree symbol). Absolute zero is 0 K (−273.15 °C). Kelvin is the SI base unit of temperature.
• 9/5 — The ratio that accounts for the different degree sizes between the Fahrenheit and Celsius scales (100 Celsius degrees span 180 Fahrenheit degrees).
• 32 — The offset constant that aligns the Celsius and Fahrenheit scales, since 0 °C equals 32 °F.
• 273.15 — The offset constant that shifts the Celsius scale to the absolute thermodynamic Kelvin scale, where 0 K is absolute zero.

Step 1 — Fahrenheit to Celsius:
°C = (98.6 − 32) × 5/9
°C = 66.6 × 5/9
°C = 333/9
°C = 37.0 °C

Step 2 — Celsius to Kelvin:
K = 37.0 + 273.15
K = 310.15 K

Result: 98.6 °F = 37.0 °C = 310.15 K

The result confirms that normal human body temperature is exactly 37 °C or 310.15 K. This is a well-known medical benchmark. The Kelvin value is useful in thermodynamic and scientific calculations where absolute temperature is required. The Celsius value is what most of the world uses clinically, while Fahrenheit is standard in the United States.

Understanding the Three Temperature Scales

Celsius (°C)

Developed by Anders Celsius in 1742, the Celsius scale sets 0 °C as the freezing point and 100 °C as the boiling point of water at sea level. It is the standard scale used by most countries worldwide for everyday temperature measurement.

Fahrenheit (°F)

Proposed by Daniel Gabriel Fahrenheit in 1724, the Fahrenheit scale sets 32 °F as the freezing point and 212 °F as the boiling point of water. It remains the primary scale used in the United States for weather forecasts, cooking, and general use.

Kelvin (K)

The Kelvin scale, defined by Lord Kelvin (William Thomson) in the 19th century, is the SI (International System of Units) base unit for thermodynamic temperature. It starts at absolute zero (0 K = −273.15 °C) — the theoretical point at which all molecular motion stops. Scientists and engineers use Kelvin in thermodynamics, astrophysics, chemistry, and material science.

Key Reference Points Across All Three Scales

| Reference Point | °C | °F | K | |---|---|---|---| | Absolute zero | −273.15 | −459.67 | 0 | | Water freezes | 0 | 32 | 273.15 | | Room temperature | ~20–22 | ~68–72 | ~293–295 | | Body temperature | 37 | 98.6 | 310.15 | | Water boils | 100 | 212 | 373.15 |

Why Do Different Countries Use Different Scales?

The Fahrenheit scale was widely adopted in English-speaking countries before the global metric standardization movement of the 20th century. The Celsius scale is part of the metric (SI) system and is now standard in science and most of the world. Kelvin is reserved for scientific and engineering precision work where absolute temperature matters.

• **Forgetting the +32 offset** when converting Celsius to Fahrenheit — multiplying by 9/5 alone gives the wrong answer.
• **Confusing the direction of subtraction** in Fahrenheit-to-Celsius: you must subtract 32 *before* multiplying by 5/9, not after.
• **Using 273 instead of 273.15** when converting to or from Kelvin — this introduces a 0.15-degree error that matters in precise scientific work.
• **Writing a degree symbol with Kelvin** (e.g., °K) — Kelvin values are written as plain 'K' without the degree symbol per SI convention.
• **Expecting negative Kelvin values** — Kelvin cannot go below 0 K (absolute zero), so any input below −273.15 °C is physically impossible.
• **Rounding too early** in a multi-step conversion (e.g., Fahrenheit → Kelvin through Celsius) — always carry full precision until the final result.

• SI Brochure: The International System of Units (9th edition) — Unit of thermodynamic temperature (kelvin) — Bureau International des Poids et Mesures (BIPM)
• NIST Special Publication 811: Guide for the Use of the International System of Units (SI) — National Institute of Standards and Technology (NIST)
• Temperature Scales and Thermometry — National Institute of Standards and Technology (NIST)

Only sources that have been reviewed are shown. Unverified citations are never published.