About

Incorrect temperature conversion causes real failures: furnace calibrations drift, chemical reactions miss target thresholds, cryogenic storage breaches safety margins. This converter implements exact arithmetic for 8 scales - Celsius, Fahrenheit, Kelvin, Rankine, Réaumur, Delisle, Newton, and Rømer - routing every conversion through T_C as the canonical intermediate. Each result is clamped against absolute zero (−273.15 °C), preventing physically meaningless outputs. The tool assumes ideal gas‐law conditions and does not model relativistic or quantum‐mechanical thermal effects.

Most online converters handle only three scales. This tool covers all historically and scientifically significant temperature scales with their exact conversion coefficients as defined by NIST and BIPM standards. Pro tip: Rankine is used extensively in US engineering thermodynamics (steam tables, HVAC); if you work in SI, you likely never need it - but when you do, an incorrect conversion factor costs hours of debugging.

Formulas

All conversions use Celsius (T_C) as the canonical intermediate. The input value is first converted to Celsius, then from Celsius to every target scale.

T_F = T_C × 95 + 32

T_K = T_C + 273.15

T_R = (T_C + 273.15) × 95

T_Ré = T_C × 45

T_De = (100 − T_C) × 32

T_N = T_C × 33100

T_Rø = T_C × 2140 + 7.5

Where T_C = temperature in Celsius, T_F = Fahrenheit, T_K = Kelvin, T_R = Rankine, T_Ré = Réaumur, T_De = Delisle (inverted scale: higher value = colder), T_N = Newton, T_Rø = Rømer. Absolute zero is enforced: T_C ≥ −273.15.

Reference Data

Scale	Symbol	Absolute Zero	Water Freezes	Water Boils	Body Temp	Inventor	Year	Primary Use
Celsius	°C	−273.15	0	100	37	Anders Celsius	1742	Global scientific & daily use
Fahrenheit	°F	−459.67	32	212	98.6	Daniel Fahrenheit	1724	USA, Cayman Islands, Liberia
Kelvin	K	0	273.15	373.15	310.15	Lord Kelvin	1848	SI base unit, thermodynamics
Rankine	°R	0	491.67	671.67	558.27	William Rankine	1859	US engineering thermodynamics
Réaumur	°Ré	−218.52	0	80	29.6	Réaumur	1730	Historic (cheese/food industry)
Delisle	°De	559.725	150	0	94.5	Joseph-Nicolas Delisle	1732	Historic (Russia, 18th century)
Newton	°N	−90.14	0	33	12.21	Isaac Newton	1701	Historic (Newton's experiments)
Rømer	°Rø	−135.90	7.5	60	26.925	Ole Rømer	1701	Historic (Fahrenheit's basis)
Planck Temp	T_P	0	≈ 0	≈ 0	≈ 0	Max Planck	1899	Theoretical physics limit
Triple Point (Water)	-	0.01 °C = 273.16 K = 32.018 °F (defined reference point, BIPM)
Absolute Zero	-	0 K = −273.15 °C = −459.67 °F = 0 °R (3rd Law of Thermodynamics)
Room Temperature	-	20 - 25 °C = 68 - 77 °F = 293.15 - 298.15 K
Solar Surface	-	5778 K = 5505 °C = 9941 °F
Liquid Nitrogen	-	−196 °C = 77.15 K = −320.8 °F
Dry Ice Sublimation	-	−78.5 °C = 194.65 K = −109.3 °F

Frequently Asked Questions

Absolute zero is the same physical point - zero molecular kinetic energy. Its numeric value differs because each scale uses a different origin and step size. In Celsius it is −273.15 °C, in Fahrenheit −459.67 °F, and in Kelvin and Rankine it is exactly 0. The converter clamps all inputs at this limit to prevent physically impossible values.

Yes. Delisle is an inverted scale: higher numeric values correspond to colder temperatures. Water boils at 0 °De and freezes at 150 °De. This tool handles the inversion correctly in both directions. Absolute zero on the Delisle scale is approximately 559.725 °De.

Rankine is the absolute temperature scale based on Fahrenheit degree increments. It appears in US engineering thermodynamics, particularly in steam tables, Rankine cycle analysis, and some ASHRAE HVAC calculations. If your reference data uses BTU and °F, Rankine maintains dimensional consistency without additional conversion factors.

This tool converts to Celsius as the intermediate and then to the target, using IEEE 754 double-precision floating-point arithmetic throughout. Results are displayed to 4 decimal places. For most engineering and scientific work this precision (0.0001 degree) exceeds measurement instrument accuracy. If you need higher precision, the underlying JavaScript Number type provides approximately 15 - 17 significant digits.

Neither scale is in active scientific or industrial use. The Newton scale (proposed by Isaac Newton around 1701) and the Rømer scale (Ole Rømer, also 1701) are historically significant - Rømer's work directly influenced Fahrenheit's calibration. They appear in history of science coursework and in validating legacy experimental records.

The converter rejects it and displays an error toast. Temperatures below absolute zero violate the Third Law of Thermodynamics under classical physics. While negative absolute temperatures exist in specialized quantum systems (population inversion in lasers), they do not map onto these classical scales in a meaningful way for general conversion.