What are the formulas between Celsius, Fahrenheit, and Kelvin?

Fahrenheit equals Celsius times 9/5 plus 32. Kelvin equals Celsius plus 273.15. To go from Fahrenheit to Celsius, subtract 32 then multiply by 5/9. Kelvin has no negative values because it starts at absolute zero, the coldest possible temperature.

Why is absolute zero important?

Absolute zero, at 0 Kelvin, minus 273.15 Celsius, or minus 459.67 Fahrenheit, is the theoretical point where particle motion reaches its minimum and thermal energy is at its lowest. It anchors the Kelvin scale and is unreachable in practice, though labs have come within billionths of a degree.

What counts as normal body temperature?

The traditional figure is 37 Celsius, or 98.6 Fahrenheit, though healthy adults range from about 36.1 to 37.2 Celsius and vary through the day. Modern studies suggest the average is slightly below the classic 37 figure, closer to 36.6 Celsius.

What is standard room temperature?

Comfortable indoor room temperature is usually defined as about 20 to 22 Celsius, or 68 to 72 Fahrenheit. Scientific standard ambient temperature is often taken as 25 Celsius (298.15 Kelvin) for reporting measurements.

Does water always boil at 100 Celsius?

Only at standard sea-level pressure. Boiling point drops with altitude as air pressure falls — water boils near 93 Celsius at 2000 metres. The 100 Celsius figure is defined at one standard atmosphere of pressure.

What is the Temperature Reference Points?

A reference table of important temperature landmarks — absolute zero, water freezing and boiling, body temperature, room temperature, and more — shown in Celsius, Fahrenheit, and Kelvin. Filter the list and convert any custom value instantly. Runs in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

Temperature Reference Points

Name: Temperature Reference Points
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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Some temperatures come up again and again — the freezing and boiling points of water, body temperature, absolute zero, room temperature. This reference lists each landmark in all three common scales (Celsius, Fahrenheit, Kelvin) and lets you convert any custom value into the same three units.

How it works

The three scales are linear transformations of one another. The conversions used throughout this tool are:

°F = °C × 9/5 + 32
K  = °C + 273.15
°C = (°F − 32) × 5/9

Kelvin is an absolute scale anchored at 0 K = absolute zero = −273.15 °C, so it never goes negative. Each reference point is stored in Celsius and converted on the fly to Fahrenheit and Kelvin for display.

Expanded reference table

Landmark	°C	°F	K	Notes
Absolute zero	−273.15	−459.67	0	Theoretical minimum
Liquid nitrogen boils	−195.8	−320.4	77.4	Common cryogen
Dry ice sublimes	−78.5	−109.3	194.6	CO₂ at 1 atm
Water freezes	0	32	273.15	1 atm standard pressure
Room temperature	~20–22	~68–72	~293–295	Comfortable indoor
Scientific standard (SATP)	25	77	298.15	Standard Ambient
Human body	~37	~98.6	~310	Core temperature, ranges ~36.1–37.2
Pasteurisation (milk)	72	161.6	345	Brief high-heat method
Water boils	100	212	373.15	1 atm
Oven (moderate)	~180	~356	~453	Typical baking
Aluminium melts	660	1220	933	Common metal benchmark
Iron melts	1538	2800	1811	Structural steel reference

Why three scales exist

Celsius was defined for everyday practical use, anchored at the phase transitions of water at sea-level pressure. It is the standard in scientific work and most of the world outside the United States.

Fahrenheit was developed earlier and remains the everyday scale in the United States and a few other countries. Its anchors were the temperature of an ice-salt mixture (0 °F) and human body temperature (96 °F in the original calibration), which is why the round Celsius numbers map to odd Fahrenheit figures.

Kelvin is the SI base unit of thermodynamic temperature. Because it starts at absolute zero, it is used in physics, chemistry, and engineering equations where negative temperature values would cause problems. The degree size is the same as Celsius, so converting between them is simply adding or subtracting 273.15 — no rescaling needed.

A quick mental anchor

Memorising a few crossover points makes Celsius-Fahrenheit conversion fast in your head: 0 °C = 32 °F (freezing), 20 °C ≈ 68 °F (pleasant room), 37 °C ≈ 99 °F (body heat), 100 °C = 212 °F (boiling). The rough doubling-minus-30 shortcut (double the Celsius and subtract 30) gives a close enough estimate for quick everyday judgements.