Temperature Scales
Temperature measures thermal energy per particle on an agreed scale. Common scales include Celsius (°C), Fahrenheit (°F), and Kelvin (K). This converter uses Kelvin as the internal reference because it is an absolute scale starting at absolute zero.
Conversion Formulas
All scales convert through Kelvin internally. Affine formulas (with offset) are required — you cannot multiply Celsius by a single factor to get Fahrenheit.
Thermodynamics Context
Kelvin is the SI base unit for thermodynamic temperature. It measures absolute thermal energy scale starting at absolute zero. Celsius and Fahrenheit are practical scales with offset zero points; Rankine uses Fahrenheit-sized degrees from absolute zero.
For related quantities, see the Energy Conversion Calculator and Pressure Converter.
Temperature Point vs Difference
Converting a temperature point (e.g., “water boils at 100 °C”) uses offset formulas. Converting a temperature difference (e.g., “increased by 10 °C”) uses different factors: 1 °C change = 1 K change = 1.8 °F change. This tool converts temperature points. A dedicated difference mode is planned for a future update.
Absolute Zero
Absolute zero is 0 K = −273.15 °C = −459.67 °F. The converter validates each scale's minimum and rejects physically impossible values.
Reference Temperatures
| Reference | °C | °F |
|---|---|---|
| Absolute zero | −273.15 | −459.67 |
| Water freezes | 0 | 32 |
| Room temperature | ≈ 20 | ≈ 68 |
| Body temperature | 37 | 98.6 |
| Water boils | 100 | 212 |
Examples
0 °C
0 °C = 32 °F = 273.15 K.
100 °C
100 °C = 212 °F = 373.15 K.
−40 °
−40 °C = −40 °F = 233.15 K.
Body temperature
37 °C ≈ 98.6 °F.
Common Mistakes
Using multiplication-only conversion (doubling °C does not double °F). Confusing temperature point conversion with interval conversion. Forgetting that Kelvin cannot be negative.
Limitations
Temperature difference conversion mode is not included in v1. Historical scales (Delisle, Newton, Rømer) are provided for reference with notes about their inverted or non-standard zero points.
FAQ
How do I convert Celsius to Fahrenheit?›
°F = °C × 9/5 + 32. Example: 0 °C = 32 °F.
How do I convert Fahrenheit to Celsius?›
°C = (°F − 32) × 5/9.
What is absolute zero?›
0 K = −273.15 °C = −459.67 °F. No temperature can be below this.
Is −40 the same in °C and °F?›
Yes. −40 °C = −40 °F exactly.
What is Rankine?›
Rankine uses Fahrenheit-sized degrees but starts at absolute zero: 0 °R = 0 K.
Temperature point vs difference?›
Converting a temperature point uses offset formulas. Temperature differences convert differently: 1 °C = 1 K = 1.8 °F change.
What is body temperature in °F?›
Normal body temperature ≈ 37 °C = 98.6 °F.
Can Kelvin be negative?›
No. This converter rejects values below 0 K.
Sources
Author & technical reviewer
Manish Kumar
PhysicsCalcs tools are reviewed with an educational focus: clear formulas, transparent assumptions, and practical context for students and science learners.
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