Temperature Converter
Convert temperatures between Celsius, Fahrenheit, and Kelvin using standard international formulas. Whether you're traveling abroad, working on science homework, or reading a recipe from another country, get instant accurate conversions between all three temperature scales.
How Temperature Conversion Works
Temperature scales measure the same physical property - molecular kinetic energy - but use different reference points and intervals. Converting between them requires specific formulas based on each scale's definition.
Think of it like translating languages: the underlying concept (temperature) is the same, but different scales express it using different "words" (numbers). The formulas are the dictionaries that let you translate between them.
°C = (32 - 32) × 5/9 = 0 × 5/9 = 0°C
Where:
- °C (Celsius): Temperature scale based on water's freezing (0°) and boiling (100°) points at sea level
- °F (Fahrenheit): Temperature scale with water freezing at 32° and boiling at 212°
- K (Kelvin): Absolute temperature scale starting at absolute zero (0 K = -273.15°C)
- 9/5 and 5/9: Conversion ratios between Celsius and Fahrenheit degree sizes
- 32: Offset between Fahrenheit and Celsius zero points
- 273.15: Offset between Kelvin and Celsius zero points
Common Temperature Reference Chart
Here are everyday temperatures expressed in all three scales to help you build intuition for each system:
| Condition | Celsius (°C) | Fahrenheit (°F) | Kelvin (K) |
|---|---|---|---|
| Absolute Zero | -273.15 | -459.67 | 0 |
| Coldest Natural Earth Temp | -89.2 | -128.6 | 184 |
| Dry Ice | -78.5 | -109.3 | 194.7 |
| Average Winter Day (Cold) | -10 | 14 | 263.15 |
| Water Freezes | 0 | 32 | 273.15 |
| Cold Day | 10 | 50 | 283.15 |
| Room Temperature | 20-22 | 68-72 | 293-295 |
| Warm Day | 30 | 86 | 303.15 |
| Human Body Temperature | 37 | 98.6 | 310.15 |
| Hot Summer Day | 40 | 104 | 313.15 |
| Water Boils | 100 | 212 | 373.15 |
| Baking Cookies | 175 | 350 | 448.15 |
| Self-Cleaning Oven | 480 | 900 | 753.15 |
Real-World Temperature Conversion Scenarios
📺 Weather Forecast: International Travel
- Situation: You're traveling from the U.S. to Europe
- U.S. Forecast: 75°F
- European Equivalent: 24°C
Key Insight: 75°F (24°C) is pleasant spring weather. You'll want light layers - not quite shorts weather but definitely no heavy jacket needed. Most comfortable outdoor temperatures worldwide fall between 20-25°C (68-77°F).
🍳 Cooking: Recipe Translation
- British Recipe: Bake at 180°C
- Your American Oven: 356°F (set to 350°F)
- Result: Perfectly baked goods
Key Insight: 180°C equals 356°F, which you'd round to 350°F on most ovens. Common international baking temperatures: 160°C (325°F) for slow baking, 180°C (350°F) standard, 200°C (400°F) for roasting.
🔬 Science Lab: Chemistry Experiment
- Lab Instructions: Heat solution to 298 K
- Celsius Equivalent: 25°C
- Fahrenheit: 77°F
Key Insight: Scientific work uses Kelvin because it's an absolute scale (no negative numbers) and maintains proportional relationships. 298 K is slightly above room temperature - warm but not hot to the touch.
🏊 Pool Temperature: Comfortable Swimming
- Pool Temperature: 82°F
- Celsius: 28°C
- Feel: Comfortably warm for swimming
Key Insight: Most people find 26-30°C (79-86°F) comfortable for swimming. Below 24°C (75°F) feels cool, while above 32°C (90°F) feels like bathwater. Competition pools are typically kept at 25-28°C.
Understanding the Three Temperature Scales
🌡️ Celsius (°C)
Origin: Created by Swedish astronomer Anders Celsius in 1742, based on water's properties at sea level.
Used By: Most of the world (195+ countries), scientific community (except for specific Kelvin use cases).
Key Points: 0°C = water freezes, 100°C = water boils. Intuitive decimal system aligned with metric measurements.
Example: A comfortable room is 20°C, body temperature is 37°C, a hot day is 35°C.
🇺🇸 Fahrenheit (°F)
Origin: Created by Daniel Gabriel Fahrenheit in 1724. Originally, 0°F was the coldest temperature Fahrenheit could create with ice and salt.
Used By: United States, some Caribbean nations, and Liberia. Used for body temperature worldwide (98.6°F standard).
Key Points: 32°F = water freezes, 212°F = water boils. Smaller degrees (1.8× more precise than Celsius) make daily weather reporting more granular.
Example: Room temperature is 70°F, body temp is 98.6°F, a hot day is 95°F.
🔬 Kelvin (K)
Origin: Named after Lord Kelvin (William Thomson) in 1848. Based on absolute zero, the theoretical coldest possible temperature.
Used By: Scientists, engineers, and physicists worldwide. The SI unit for thermodynamic temperature.
Key Points: 0 K = absolute zero (-273.15°C), no negative numbers. Same degree size as Celsius, just offset by 273.15.
Example: Room temperature is 293 K, water boils at 373 K, outer space is about 3 K.
📊 Scale Comparison
Degree Size: Celsius and Kelvin have identical degree sizes. Fahrenheit degrees are 5/9 the size of Celsius degrees (1°C = 1.8°F).
Zero Points: Celsius: water's freezing point. Fahrenheit: coldest brine temperature. Kelvin: absolute zero.
Practical Range: Celsius: -50 to 50°C for everyday use. Fahrenheit: -60 to 120°F daily. Kelvin: 200 to 400 K for common temperatures.
Example: A 10° change: +10°C = +18°F = +10 K (same magnitude, different reference points).
Smart Temperature Conversion Tips
💡 Quick Mental Math: Celsius to Fahrenheit
For rough conversions, double the Celsius temperature and add 30. For example, 20°C: (20 × 2) + 30 = 70°F. The actual answer is 68°F, so you're within 2 degrees - good enough for everyday decisions.
Why it works: The precise formula multiplies by 1.8 (close to 2) and adds 32 (close to 30). The approximation trades precision for speed.
💡 Quick Mental Math: Fahrenheit to Celsius
Subtract 30 and divide by 2. For 80°F: (80 - 30) ÷ 2 = 25°C. Actual answer is 26.7°C - close enough for most purposes. For more accuracy, subtract 32 instead of 30.
Why it works: You're reversing the Celsius-to-Fahrenheit approximation. Using 32 instead of 30 gets you within 1 degree usually.
💡 Celsius to Kelvin is Simple Addition
Just add 273.15 to any Celsius temperature. Room temperature (20°C) becomes 293.15 K. This is the easiest conversion because both scales use the same degree size.
Why it works: Kelvin is literally Celsius shifted by 273.15 degrees. The degree intervals are identical - only the starting point (zero) differs.
💡 Memorize Key Reference Points
Learn these anchors: 0°C = 32°F (freezing), 10°C = 50°F (cool), 20°C = 68°F (room temp), 30°C = 86°F (hot), 37°C = 98.6°F (body temp), 100°C = 212°F (boiling).
Why it works: With these memorized, you can interpolate temperatures between them. If it's 25°C, you know it's between 68°F and 86°F - about 77°F.
💡 Use the -40 Trick
-40°C and -40°F are the same temperature! This is the one point where both scales intersect. It's also really, really cold - colder than most people will ever experience.
Why it works: The formulas cross at this exact point: (-40 × 9/5) + 32 = -40. Mathematically inevitable, practically useless but fun to know.
💡 Scientific Work? Always Use Kelvin
When doing calculations involving gas laws, thermal physics, or any equation with temperature ratios, convert to Kelvin first. Celsius and Fahrenheit can give wrong answers in ratio calculations.
Why it works: Kelvin is an absolute scale. 20 K is actually twice as hot as 10 K. But 20°C is not twice as hot as 10°C (both are similar room temperatures).
⚠️ Common Temperature Conversion Mistakes
🚩 Forgetting to Convert Before Calculations
The Mistake: Using Celsius or Fahrenheit temperatures directly in scientific equations without converting to Kelvin first.
Why It Matters: In thermodynamics, temperature ratios only work with absolute scales (Kelvin). Using Celsius/Fahrenheit in equations like PV=nRT gives completely wrong results.
What To Do Instead: Always convert to Kelvin (K = °C + 273.15) before plugging into scientific equations. Convert back to your preferred scale after calculations.
🚩 Confusing Temperature Differences with Actual Temperatures
The Mistake: Thinking a 10°C increase equals an 18°F increase because 1°C = 1.8°F in the conversion formula.
Why It Matters: Temperature differences convert differently than absolute temperatures. A 10°C rise equals an 18°F rise, but 10°C ≠ 18°F (it's actually 50°F).
What To Do Instead: For temperature differences, multiply Celsius changes by 1.8 without adding 32. For absolute temperatures, use the full formula with the +32 offset.
🚩 Rounding Too Early in Multi-Step Conversions
The Mistake: Converting 25°C to Fahrenheit (77°F), rounding to 80°F, then converting back to Celsius and getting 27°C instead of 25°C.
Why It Matters: Each rounding step compounds errors. In recipes or scientific work, even 2-3 degrees can matter significantly.
What To Do Instead: Keep at least 2 decimal places throughout calculations. Only round your final answer. If doing multiple conversions, use the full precision throughout.
🚩 Using Kelvin with a Degree Symbol
The Mistake: Writing "25°K" instead of "25 K" when referring to temperature in Kelvin.
Why It Matters: Kelvin is an absolute scale, not a degree-based scale. The proper notation is "K" without the degree symbol (°). Using °K marks you as unfamiliar with scientific conventions.
What To Do Instead: Always write Kelvin as just "K" - for example, "273 K" not "273°K". Write Celsius as °C and Fahrenheit as °F (both use the degree symbol).
Sources & Methodology
National Institute of Standards and Technology (NIST)
Temperature scale definitions and conversion formulas verified against NIST Special Publication 811, which provides official guidelines for the International System of Units (SI) as used in the United States.
View Source →International Bureau of Weights and Measures (BIPM)
The Kelvin temperature scale definition based on the SI Brochure (9th edition, 2019), which establishes the kelvin as one of the seven base units in the International System of Units.
View Source →National Weather Service
Common temperature reference points and weather-related conversions sourced from official NWS documentation and educational materials on temperature measurement standards.
View Source →How to Use This Calculator
- Enter Your Temperature Value: Type the temperature you want to convert into the "Temperature Value" field. You can use whole numbers or decimals (e.g., 32 or 98.6).
- Select Your Starting Unit: Use the "From Unit" dropdown to choose whether your input is in Celsius (°C), Fahrenheit (°F), or Kelvin (K).
- Choose Your Target Unit: Use the "To Unit" dropdown to select which temperature scale you want to convert to. You can convert between any combination of the three scales.
- Calculate: Click the "Convert" button or press Enter on your keyboard. The converted temperature will appear immediately in a highlighted result box.
- Review the Result: The result shows your converted temperature with 2 decimal places for accuracy, along with a description of the conversion performed.
- Reference the Chart: Scroll down to the Common Temperature Reference Chart to see how your converted temperature relates to everyday reference points.
Common Questions
Celsius and Fahrenheit are two different scales for measuring temperature. Celsius (°C) is based on water's freezing point (0°C) and boiling point (100°C), making it a decimal-based system used worldwide. Fahrenheit (°F) places water's freezing at 32°F and boiling at 212°F, primarily used in the United States. The key difference is the scale: 1°C change equals 1.8°F change.
The United States adopted Fahrenheit before the metric system became widely used internationally. When the metric system gained global adoption in the 1960s-1970s, the U.S. began metrication efforts but they stalled due to cost, public resistance, and the complexity of changing infrastructure. Today, the U.S. is one of only three countries (along with Liberia and Myanmar) that hasn't officially adopted the metric system, though Celsius is used in scientific contexts.
Kelvin is the SI unit for temperature used primarily in scientific and engineering contexts, especially when working with absolute temperatures or thermodynamic calculations. Use Kelvin when dealing with gas laws, thermal physics, astronomy, or any calculation where temperature ratios matter. Kelvin starts at absolute zero (0 K = -273.15°C), the coldest possible temperature where molecular motion stops.
Temperature conversions using standard formulas are mathematically exact. However, practical accuracy depends on the precision of your input measurement and the instrument used. Most household thermometers are accurate within ±1-2 degrees. For scientific work requiring high precision, use calibrated instruments and maintain appropriate significant figures in your calculations.
Absolute zero is 0 Kelvin (-273.15°C or -459.67°F), the theoretical lowest possible temperature. At this point, atoms and molecules have minimal kinetic energy - they can't move slower. According to the third law of thermodynamics, absolute zero cannot be reached in practice, though scientists have gotten within billionths of a degree using advanced cooling techniques.
Disclaimer
This calculator provides temperature conversions using internationally accepted formulas from NIST and BIPM standards. While the mathematical conversions are exact, practical accuracy depends on your measurement instrument. For scientific or engineering applications requiring high precision, verify conversions using calibrated equipment and maintain appropriate significant figures throughout calculations.