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Temperature Converter

Convert Celsius, Fahrenheit, Kelvin, Rankine & 5+ temperature scales instantly. Used by cooks, meteorologists & scientists. Free, no sign-up, published conversion formulas.

Last revised 29 September 2026

By Team GlobalCalqulate · About our editorial standards

Temperature Conversion

Value

Enter the temperature value to convert. Negative values are supported.

From Unit

Select the unit you want to convert from.

To Unit

Select the unit you want to convert to.

Decimal Places

Number of decimal places for the result (max 15).

Disclaimer: These are exact temperature-scale conversions (fixed formulas such as °F = °C × 9/5 + 32), which is distinct from temperature measurement accuracy — a real thermometer or sensor's precision depends on its own calibration. Values below absolute zero (-273.15°C / 0 K) are not physically possible; results outside that bound indicate an invalid input, not a real temperature. Full disclaimer.

Sources & methodology

Formula:: Scales are affine, not proportional
Reference:: Bureau International des Poids et Mesures (BIPM)
Content last updated:: September 2026
Scheduled re-verification:: September 2027

Calculation type: Exact calculation. Figures are taken from Bureau International des Poids et Mesures (BIPM) and BIPM Consultative Committee for Thermometry (CCT) and National Institute of Standards and Technology (NIST) — see sources below.

Formula & methodology

Formula used

Scales are affine, not proportional

T/K = T/°C + 273.15;   T/°F = T/°C × 9/5 + 32;   T/K = T/°R × 5/9

Temperature conversions need an OFFSET as well as a ratio, so unlike length or mass they cannot be handled by a single factor table. Every conversion routes through the kelvin, the SI base unit of thermodynamic temperature.

Why a ratio alone fails

20 °C is not "twice as hot" as 10 °C

Because Celsius and Fahrenheit have arbitrary zero points, ratios between their readings are meaningless. Only kelvin and Rankine start at absolute zero, so only they support ratio comparisons.

Variable definitions

Symbol	Meaning	Unit
T/K	Kelvin. thermodynamic temperature; the SI base unit, starting at absolute zero	K
T/°C	Celsius. offset from kelvin by exactly 273.15	°C
T/°F	Fahrenheit. ratio 9/5 to Celsius, offset by 32	°F

Step-by-step calculation

1. Enter the temperature and its scale
The value is converted to kelvin first.
2. Choose the target scale
Kelvin is converted out, applying the offset as well as the ratio.

Limitations

The defining relations above are exact, so results are limited only by display rounding.
A temperature DIFFERENCE converts differently from a temperature. A rise of 10 °C is a rise of 18 °F, not 50 °F — the offset applies to a reading, never to an interval.
Below absolute zero (0 K, −273.15 °C) there is no physical temperature; such an input is arithmetic, not a real state.

This page is educational. It converts between units using the defined or standard factors shown above, so the arithmetic is exact to the precision displayed — but a converted value is only as good as the measurement behind it, and some units are defined only under stated conditions. Where a conversion is safety-critical or contractual, check it against the governing standard rather than relying on this page.

Sources & references

The International System of Units (SI Brochure, 9th edition) — Bureau International des Poids et Mesures (BIPM)
Guides to Thermometry and the International Temperature Scale of 1990 (ITS-90) — BIPM Consultative Committee for Thermometry (CCT)
NIST Special Publication 811: Guide for the Use of the International System of Units — Appendix B.6, exact conversion factors — National Institute of Standards and Technology (NIST)

Verified against internationally recognized measurement standards (BIPM SI Brochure, NIST, and other applicable standards); see the sources above for the specific documents used. Every factor on this page is exact by definition rather than an empirical measurement, except where the page says otherwise — so results are limited only by the display rounding you choose. Standards review: August 2026. Temperature scales are affine, so each conversion applies an offset as well as a ratio; all defining relations used are exact.

Help & FAQs

Frequently Asked Questions

Clear answers to common questions to help you use this calculator confidently.

How do I convert Celsius to Fahrenheit?

Tap to view the answer

Formula: °F = (°C × 9/5) + 32. Example: 25°C = 77°F. For a quick estimate, double °C and add 30 (25 × 2 + 30 = 80, close to the exact 77).

How do I convert Fahrenheit to Celsius?

Tap to view the answer

Formula: °C = (°F − 32) × 5/9. Example: 98.6°F = 37°C, which is normal human body temperature.

What is absolute zero, and why can't temperature go lower?

Tap to view the answer

Absolute zero — 0 K, -273.15°C, -459.67°F — is the lowest temperature theoretically possible, where particles have minimal thermal motion. No physical temperature can go below it, so a converted result below this bound indicates an invalid input rather than a real temperature.

How do I convert Celsius to Kelvin?

Tap to view the answer

Formula: K = °C + 273.15. Example: 0°C = 273.15 K, 25°C = 298.15 K. Kelvin is the SI absolute scale used in science and never goes negative.

Is this temperature converter accurate for science and cooking?

Tap to view the answer

Yes — the conversion formulas are exact and match NIST/BIPM definitions, so results are limited only by your chosen decimal places. This covers cooking, weather, and general engineering; note that conversion accuracy is separate from a thermometer or sensor's own measurement accuracy, which depends on its calibration.

Need more help? Contact support or email globalcalqulate@gmail.com

We typically reply within 24–48 hours.

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How to Use This Calculator

Enter Temperature Value

Type the numeric temperature value you want to convert, such as an oven setting or a weather reading.

Select Source Unit

Choose the scale your reading is in (e.g., Celsius for a weather forecast, Fahrenheit for a US recipe).

Select Target Unit

Choose the scale you want to convert to (e.g., Fahrenheit, Kelvin, or Rankine).

View Results

See the converted value, formula, and real‑world context.

Common Celsius to Fahrenheit equivalents
Celsius (°C)	Fahrenheit (°F)
-40	-40
-20	-4
0	32
10	50
20	68
25	77
30	86
37	98.6
40	104
50	122
60	140
70	158
80	176
90	194
100	212
150	302
200	392

Celsius (°C)

Fahrenheit (°F)

-40

-20

-4

98.6

104

122

140

158

176

194

100

212

150

302

200

392

Understanding Your Results

Celsius (°C)
The metric temperature scale where water freezes at 0°C and boils at 100°C. Used worldwide for everyday temperature.
Fahrenheit (°F)
The imperial temperature scale where water freezes at 32°F and boils at 212°F. Used mainly in the US.
Kelvin (K)
The SI unit of temperature. Absolute zero is 0 K. Used in science and physics. K = °C + 273.15.
Rankine (°R)
The absolute temperature scale with Fahrenheit-sized degrees. 0°R = absolute zero. Used in engineering.

Key Tips

✓
°F = (°C × 9/5) + 32; to convert Celsius to Fahrenheit, multiply by 9/5 and add 32.
✓
°C = (°F - 32) × 5/9; to convert Fahrenheit to Celsius, subtract 32 and multiply by 5/9.
✓
K = °C + 273.15; to convert Celsius to Kelvin, add 273.15.
✓
Normal body temperature: 37°C = 98.6°F = 310.15 K.
✓
Water boils at 100°C = 212°F = 373.15 K at sea level.
✓
Absolute zero: 0 K = -273.15°C = -459.67°F.

Understanding Temperature Scales

What is Temperature?

Temperature reflects the average kinetic energy of a substance's particles. Celsius and Fahrenheit are offset scales with different zero points; Kelvin is the SI unit, starting at absolute zero (−273.15°C), the theoretical point where particle motion stops.

Common Temperature Scales

Celsius and Fahrenheit are used for everyday temperatures. Kelvin is the SI unit for science. Rankine is used in engineering thermodynamics.

Absolute Zero

Absolute zero is the lowest possible temperature where particles have minimal thermal motion. It is 0 K, -273.15°C, -459.67°F.

Formula & methodology

Formula used

Scales are affine, not proportional

T/K = T/°C + 273.15;   T/°F = T/°C × 9/5 + 32;   T/K = T/°R × 5/9

Why a ratio alone fails

20 °C is not "twice as hot" as 10 °C

Because Celsius and Fahrenheit have arbitrary zero points, ratios between their readings are meaningless. Only kelvin and Rankine start at absolute zero, so only they support ratio comparisons.

Variable definitions

Symbol	Meaning	Unit
T/K	Kelvin. thermodynamic temperature; the SI base unit, starting at absolute zero	K
T/°C	Celsius. offset from kelvin by exactly 273.15	°C
T/°F	Fahrenheit. ratio 9/5 to Celsius, offset by 32	°F

Step-by-step calculation

1. Enter the temperature and its scale
The value is converted to kelvin first.
2. Choose the target scale
Kelvin is converted out, applying the offset as well as the ratio.

Limitations

The defining relations above are exact, so results are limited only by display rounding.
A temperature DIFFERENCE converts differently from a temperature. A rise of 10 °C is a rise of 18 °F, not 50 °F — the offset applies to a reading, never to an interval.
Below absolute zero (0 K, −273.15 °C) there is no physical temperature; such an input is arithmetic, not a real state.

Sources & references

Calculator inputs

Temperature Conversion

Your results

Sources & methodology

Formula & methodology

Formula used

Scales are affine, not proportional

Why a ratio alone fails

Variable definitions

Step-by-step calculation

Limitations

Sources & references

How do I convert Celsius to Fahrenheit?

How do I convert Fahrenheit to Celsius?

What is absolute zero, and why can't temperature go lower?

How do I convert Celsius to Kelvin?

Is this temperature converter accurate for science and cooking?

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Calculator inputs

Temperature Conversion

Your results

Sources & methodology

How to Use This Calculator

Example: Convert 100°C to Fahrenheit

Common °C to °F Conversions

Understanding Your Results

Key Tips

Understanding Temperature Scales

What is Temperature?

Common Temperature Scales

Absolute Zero

Formula & methodology

Formula used

Scales are affine, not proportional

Why a ratio alone fails

Variable definitions

Step-by-step calculation

Limitations

Sources & references

How to Use This Calculator

Example: Convert 100°C to Fahrenheit

Common °C to °F Conversions

Understanding Your Results

Key Tips

Understanding Temperature Scales

What is Temperature?

Common Temperature Scales

Absolute Zero