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Temperature Converter

Measurement

Free online temperature converter. Convert between Celsius, Fahrenheit, Kelvin, and Rankine instantly. Covers body temperature and oven settings.

Reviewed by the thecalcu.com team · Last updated June 28, 2026

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What is a Temperature?

A temperature converter translates readings between the world's temperature scales, Celsius (°C), Fahrenheit (°F), Kelvin (K), and Rankine (°R). Temperature conversion is more complex than most unit conversions because scales differ not only in unit size but also in where they place zero: Celsius and Fahrenheit are relative scales (zero is not the coldest possible temperature), while Kelvin and Rankine are absolute scales anchored at absolute zero.

India uses Celsius exclusively for weather forecasts, medicine, and everyday conversation. The United States uses Fahrenheit for weather and cooking. Science and engineering globally use Kelvin for thermodynamics and physics. When a temperature from one context appears in another, an American oven recipe in Fahrenheit, a medical reference from the UK, a physics textbook using Kelvin, the conversion must handle both the scale factor and the offset correctly.

Temperature context matters significantly in India. A 45°C day in Delhi in June is a severe heat event; expressing it as 113°F helps communicate that severity to international colleagues. A fever of 102°F on an imported thermometer means 38.9°C, just above the 38°C threshold for fever medication in Indian paediatric guidelines. These conversions have real consequences.

For recipe work alongside temperature, the Volume Converter handles US cups and fluid ounces, and the Area Converter covers property measurements if you are working across mixed-unit documents.

Why Use a Temperature Converter?

The Celsius-to-Fahrenheit formula, °F = (°C × 9/5) + 32, is simple to remember but tedious to compute for non-round numbers. What is 36.8°C in Fahrenheit? (98.24°F.) What is 425°F in Celsius for a baking recipe? (218.3°C.) These require a calculator regardless, and a dedicated converter removes the risk of applying the formula backwards or misplacing the 32.

Kelvin conversions are particularly prone to error because the formula looks simple (K = °C + 273.15) but the intermediate numbers become large. For cryogenic applications near −200°C (73.15 K), or for astrophysics temperatures in the thousands of Kelvin, arithmetic errors are easy to make and hard to spot.

For Indian users cooking from international recipes, oven temperatures are the most practical daily need. Older British and American recipes specify oven settings in Fahrenheit, a 350°F oven is 176.7°C, typically set to 175°C on Indian OTGs and conventional ovens.

Who Should Use This Calculator?

Home cooks and bakers adapting American or British recipes that give oven temperatures in Fahrenheit, where Indian and European ovens use Celsius. Knowing that 350°F = 177°C and 400°F = 204°C are the two most common baking temperatures eliminates guesswork.

Healthcare professionals and patients interpreting temperature readings from international medical literature, imported drug package inserts, or digital thermometers manufactured for the US market that report in Fahrenheit.

Students and researchers in physics and chemistry who work with Kelvin for thermodynamics equations, reaction rate calculations, or spectroscopic data where absolute temperature is required.

Travellers and NRIs checking weather for Fahrenheit-reporting destinations (primarily the US and a few Caribbean countries), or Indian expats interpreting news coverage of Indian heatwaves that use Celsius.

Engineers and HVAC professionals who encounter temperature tolerances and setpoints specified in different scales across international equipment specifications and installation documents.

What Insights Does the Temperature Converter Give You?

The converted value is shown immediately as you type. For weather and cooking, 1–2 decimal places is the appropriate precision. For clinical use, where 37.0°C versus 37.5°C is a meaningful medical difference, the converter displays full decimal precision.

The reference table shows the same temperature in all four scales simultaneously. Seeing that 37°C = 98.6°F = 310.15 K = 558.27°R provides the complete scientific and everyday picture at once. For the four reference temperatures most Indian users need, water freezes (0°C/32°F), normal body temp (37°C/98.6°F), fever threshold (38°C/100.4°F), water boils (100°C/212°F), the table gives instant context.

How to use this Temperature calculator

  1. Enter the temperature value in the FROM field. Negative values are valid, Celsius and Fahrenheit frequently go below zero.
  2. Select the FROM scale, Celsius, Fahrenheit, Kelvin, or Rankine.
  3. Select the TO scale for your target measurement.
  4. Read the result instantly in the TO field. The reference table below shows all four scales simultaneously.
  5. Type in the TO field to reverse-convert, enter the target temperature and the FROM field back-calculates.
  6. Swap, the ⇅ button reverses FROM and TO while preserving the entered value.

Formula & Methodology

Temperature conversion is non-linear. The converter routes all conversions through Celsius as an intermediate step:

Celsius ↔ Fahrenheit:
- °F = (°C × 9/5) + 32
- °C = (°F − 32) × 5/9

Celsius ↔ Kelvin:
- K = °C + 273.15
- °C = K − 273.15

Celsius ↔ Rankine:
- °R = (°C + 273.15) × 9/5
- °C = (°R − 491.67) × 5/9

All other scale combinations (e.g. Fahrenheit to Kelvin) convert to Celsius first, then to the target scale.

Common reference temperatures:

| Description | Celsius | Fahrenheit | Kelvin |
|---|---|---|---|
| Absolute zero | −273.15°C | −459.67°F | 0 K |
| Water freezes | 0°C | 32°F | 273.15 K |
| Normal body temp | 37°C | 98.6°F | 310.15 K |
| Fever threshold | 38°C | 100.4°F | 311.15 K |
| Water boils | 100°C | 212°F | 373.15 K |
| Delhi peak summer | 45°C | 113°F | 318.15 K |

Worked example, interpreting a fever reading:

A child's temperature is recorded as 103°F on an imported US thermometer. Converting to Celsius:

°C = (103 − 32) × 5/9 = 71 × 5/9 = 39.44°C

This is significantly above the 38°C fever threshold, and above the 39°C level that warrants prompt medical evaluation in most Indian paediatric guidelines. The conversion changes the clinical picture from an ambiguous Fahrenheit number to a clearly actionable Celsius reading.

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Frequently Asked Questions

A temperature converter translates temperature readings between different scales, Celsius, Fahrenheit, Kelvin, and Rankine. Unlike most unit conversions, temperature scales differ in both their unit size and their zero point, so the conversion requires both multiplication and addition rather than a simple factor. The converter handles the full formula automatically for any scale combination.
To convert Celsius to Fahrenheit, multiply by 9/5 and add 32: °F = (°C × 9/5) + 32. For example, 100°C = (100 × 1.8) + 32 = 212°F. To reverse, subtract 32 then multiply by 5/9: °C = (°F − 32) × 5/9.
37°C converts to exactly 98.6°F, the classic normal human body temperature. A reading of 37.5°C (99.5°F) or above is typically considered a low-grade fever in adults, while 38°C (100.4°F) and above is classified as fever by most medical guidelines used in India.
100°F equals approximately 37.78°C. In weather terms, a 100°F summer day, common in Rajasthan and parts of UP during May and June, represents a severe heat event. India's IMD reports temperatures in Celsius, so this conversion helps when comparing Indian and US weather reports or news coverage.
Celsius and Fahrenheit are equal at −40°. Both scales read −40 at that exact point, making it a useful mental anchor for understanding how the two scales relate. Below −40 the Fahrenheit number is smaller than the Celsius number; above −40 Fahrenheit is always the larger number.
Celsius defines 0° as water's freezing point and 100° as its boiling point, giving a 100-degree span across the water phase change. Fahrenheit defines 32° as freezing and 212° as boiling, a 180-degree span. One Celsius degree therefore represents 1.8 Fahrenheit degrees of temperature change.
Normal adult body temperature is typically cited as 37°C (98.6°F), but the normal range is 36.1°C to 37.2°C (97°F to 99°F) depending on time of day and measurement method. Indian paediatric guidelines generally define fever as 38°C (100.4°F) or above, which corresponds to 100.4°F.
Water boils at 212°F (100°C) at standard atmospheric pressure at sea level. At higher altitudes, such as Shimla at 2,200 m or Leh at 3,500 m, reduced air pressure lowers the boiling point to approximately 92°C and 87°C respectively, which increases cooking times for boiled and steamed foods.
Kelvin is the SI base unit for temperature, starting at absolute zero (−273.15°C), the coldest theoretically possible temperature. Unlike Celsius and Fahrenheit, Kelvin has no negative values. It is used in physics, chemistry, astrophysics, and engineering where absolute temperature matters, thermodynamics calculations, blackbody radiation, and cryogenic systems all require Kelvin.
Absolute zero is 0 Kelvin, which equals −273.15°C or −459.67°F. This is the theoretical minimum temperature at which all molecular motion ceases. It has never been achieved experimentally, though laboratories have reached within billionths of a degree of it.
A quick approximation: double the Celsius temperature and add 30. For example, 25°C → (25 × 2) + 30 = 80°F (actual: 77°F). This slightly overestimates but is accurate enough for weather conversation. For body temperature, remembering that 37°C = 98.6°F and 38°C = 100.4°F gives reliable clinical reference anchors.
0°C equals 32°F, the freezing point of water. Any Fahrenheit reading below 32 means below-freezing conditions. Sub-zero Celsius temperatures occur in Ladakh, Himachal Pradesh, and Uttarakhand during winter months, reaching −20°C (−4°F) or below in Leh.
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