Convert Fahrenheit to Celsius – Temperature Converter
This tool converts a single temperature value from degrees Fahrenheit (°F) to degrees Celsius (°C) using the exact linear relationship between the two scales. It is intended for everyday conversions, engineering checks, and documentation where a reliable numeric translation is required.
Conversions returned are mathematical results; for measurements taken with instruments, review instrument specification sheets and calibration records. For precision-critical work (laboratory calibration, regulatory reporting, process control), follow recognized standards and calibration procedures rather than treating the conversion alone as a measurement assurance step.
Interactive Converter
Convert between fahrenheit and celsius with precision rounding.
Quick reference table
| Fahrenheit | Celsius |
|---|---|
| 1 °F | -17.22 °C |
| 5 °F | -15 °C |
| 10 °F | -12.22 °C |
| 25 °F | -3.89 °C |
| 50 °F | 10 °C |
| 100 °F | 37.78 °C |
Methodology
The Fahrenheit-to-Celsius conversion is a fixed linear transformation derived from the definition of the two temperature scales. The converter applies the exact arithmetic formula Celsius = (Fahrenheit − 32) × 5/9. This is an exact rational conversion and does not approximate the relationship.
While the arithmetic conversion is exact, real-world measurement accuracy depends on instrument performance, calibration traceability, and measurement uncertainty. Follow NIST guidance on temperature scales (ITS-90) and ISO/IEC 17025 requirements for calibration laboratories when traceability or documented uncertainty is required. For workplace or safety thresholds consult applicable OSHA guidance.
Worked examples
32 °F → (32 − 32) × 5/9 = 0 °C
212 °F → (212 − 32) × 5/9 = 100 °C
-40 °F → (-40 − 32) × 5/9 = -40 °C
Further resources
Expert Q&A
Is the conversion formula exact or approximate?
The formula °C = (°F − 32) × 5/9 is an exact linear relationship between the two scales. Any difference you see is due to rounding for display, not the formula itself.
How many decimal places should I use for reporting?
Choose decimal precision based on context and instrument uncertainty. Typical practical reporting is 0.1 °C for weather data, 0.01 °C or better for laboratory work if instruments support that precision. Always align reported precision with measured uncertainty from calibration certificates (ISO/IEC 17025).
Does this tool compensate for instrument calibration or measurement error?
No. This converter performs only the mathematical unit conversion. For calibrated measurements, apply instrument corrections and uncertainty budgets from calibration records before or after conversion as appropriate.
Can I convert negative temperatures and values below freezing?
Yes. The formula applies across the full numeric range of the two scales, including negative values and extremes approaching absolute zero. For temperatures near absolute zero, ensure your instruments and procedures are appropriate.
How does this relate to Kelvin?
To convert Fahrenheit to Kelvin, first convert Fahrenheit to Celsius with this formula, then add 273.15 to convert Celsius to Kelvin. Kelvin is the SI base unit for thermodynamic temperature.
Sources & citations
- NIST — International Temperature Scale of 1990 (ITS-90) — https://www.nist.gov/programs-projects/international-temperature-scale-1990-its-90
- ISO/IEC 17025 — General requirements for the competence of testing and calibration laboratories — https://www.iso.org/standard/66912.html
- OSHA — Heat Stress and Heat-Related Illnesses guidance — https://www.osha.gov/heat-exposure
- IEEE Instrumentation & Measurement Society — https://ieee-ims.org/