Temperature Converter
Celsius, Fahrenheit and Kelvin, with site temperature references.
Quick answer
With the default inputs: Temperature 20 · From unit CelsiusDegrees Celsius 20 °C
Edit the inputs below to recalculate.Inputs
Result
Degrees Celsius
20°C
| Degrees Fahrenheit | 68°F |
| Kelvin | 293.15K |
| Degrees Rankine | 527.67°R |
| Above freezing | 20K |
| State of water | Liquid |
| Concrete curing | Normal curing |
| Asphalt placement | Suitable |
Celsius and Fahrenheit are linear but have different zeros, so they are not proportional: 0°C = 32°F, 100°C = 212°F, and a 1°C interval equals a 1.8°F interval. Kelvin starts at absolute zero, 0 K = −273.15°C, and is used in science rather than on site.
Reverse: known result, work out one input
Enter a target result; the other inputs stay fixed and this one is worked out.
Formula
| Celsius to Fahrenheit | °F = °C × 1.8 + 32 |
| Fahrenheit to Celsius | °C = (°F − 32) ÷ 1.8 |
| Celsius to Kelvin | K = °C + 273.15 |
| Kelvin to Celsius | °C = K − 273.15 |
| Rankine | °R = (°C + 273.15) × 1.8 |
| Intervals | Δ1°C = Δ1.8°F — only differences scale |
20°C is 68°F, 293.15 K or 527.67 °R. At 5°C concrete cures normally; at −2°C it needs insulating or heating, or the early frost damage permanently reduces strength.
Temperatures that matter on site
| Temperature | Situation | Requirement |
|---|---|---|
| 0°C | Freezing point | Water freezes; concrete needs frost protection |
| 5°C | Winter concreting | Winter rules apply below 5°C for five consecutive days |
| 10°C | Asphalt placement | Not normally placed below 10°C |
| 20°C | Cube curing | Standard curing at 20 ± 2°C |
| 60°C | Steam curing cap | Usually not above 60°C to avoid strength regression |
| 100°C | Boiling point | Water boils at atmospheric pressure |
How to work it out
- Distinguish a temperature from a temperature difference first. 20°C is a point on the scale; a 20°C difference is a different quantity, and the two convert differently. This is the central distinction in temperature conversion.
- Celsius to Fahrenheit (points): ℉ = ℃ × 1.8 + 32, and ℃ = (℉ − 32) ÷ 1.8. So 20°C is 68°F, 100°C is 212°F and 0°C is 32°F.
- Celsius to kelvin (points): K = ℃ + 273.15 and ℃ = K − 273.15. Absolute zero is 0 K = −273.15°C.
- Differences scale without offset: Δ1°C = Δ1.8°F and Δ1 K = Δ1°C. A 20°C difference is a 36°F difference. Conductivity and expansion coefficients use differences.
- Rankine: °R = (℃ + 273.15) × 1.8, the absolute scale on the Fahrenheit interval, occasionally seen in Anglo-American thermal data.
- Useful reference points: concrete standard curing 20±2°C, winter concreting threshold 5°C, asphalt mixing 150-165°C, hot-water heating 75/50°C flow and return.
Where it goes wrong
- Adding 32 to a difference. Converting a 20°C difference as 20 × 1.8 + 32 = 68°F nearly doubles it; the correct figure is 36°F. Heating loads, radiator outputs and expansion all go wrong.
- Treating 0°C as 0°F. 0°C is 32°F and 0°F is −17.8°C; confusing them inverts refrigeration control settings.
- Assuming kelvin and Celsius can be mixed freely. Their intervals match, so differences may be mixed, but absolute temperatures require adding 273.15.
- Reading the winter concreting 5°C as a daily mean. The code triggers winter working when the daily mean stays below 5°C for five consecutive days — the five-day condition is part of the rule.
- Confusing placing temperature with curing temperature. Concrete must be placed at no less than 5°C and cured within limits too; they are separate control points measured separately.
Material and cost
A temperature error in concrete is a quality failure: without antifreeze admixture or adequate protection, frozen young concrete loses 30-50% of its strength permanently and must be broken out. In HVAC it is an energy problem — a doubled temperature difference doubles the plant and radiator sizes in the wrong direction.
On site
- Mental conversion: double Celsius and subtract 10%, then add 32. For 20°C: 40 − 4 = 36, plus 32 gives 68. Reverse by subtracting 32, halving and adding 10%.
- Asphalt and membrane heat resistance is given in °C on Chinese data and °F on Anglo-American products. 150°C is 302°F, not 150°F.
- Cold chain, cold storage, pharmaceutical and food standards often use °F while Chinese drawings use °C. Agree a conversion convention before cross-trade work.
- Match instrument range to the task: −10 to 50°C suits concrete curing, whereas a 0-300°C industrial gauge lacks the resolution.
Basis
- GB/T 3100-3102 Quantities and units series
- GB 50666-2011 Code for construction of concrete structures, winter working
- GB 50736-2012 Design code for heating, ventilation and air conditioning of civil buildings, heating
FAQ
Why can't Celsius be doubled to get Fahrenheit?
Because the zeros differ: 0°C is 32°F, not 0°F, so the offset must be applied before scaling. The “double and add 30” shortcut is only a rough estimate — 2°C out near 20°C but 12°C out near 100°C, useless for measuring asphalt or concrete temperature.
What temperature triggers winter concreting rules?
Winter rules apply when the daily mean stays below 5°C for five consecutive days. Then thermal blankets, heated enclosures or antifreeze admixtures are required, with placing temperature not below 5°C (2°C for mass concrete). The earlier and colder the freeze, the greater and more permanent the strength loss.
Kelvin and Celsius differ by a constant, so why keep both?
Kelvin starts at absolute zero, which physics formulas such as the ideal gas law and radiation laws require, otherwise negatives break the equations. Celsius puts zero at the freezing point of water, which suits daily use, and site work, material standards and codes all use it. The conversion is simply 273.15.
Cite this page
Use this format in reports, method statements or coursework. The link is permanent.
Building Calculator. Temperature Converter. 2026-10-25. https://jianzhujisuan.com/en/unit-temperature
Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.