Radiator ΔT converter
The calculator needs JavaScript. The worked example, formula and figures below show exactly how it works, so you can do the sum yourself. A guide, not advice. Check your supplier's or maker's figures before ordering.
Short answer
Worked example
| You enter | Value |
|---|---|
| What do you know? | The ΔT50 rating |
| Output at ΔT50 | 2,000 W |
| ΔT | 30 K |
| Radiator exponent n | 1.3 |
Output at ΔT30: 1,030 W
| Result | Value |
|---|---|
| Output at your ΔT | 1,030 W (3,513 BTU/h) |
| Output at ΔT50 | 2,000 W (6,824 BTU/h) |
| Correction factor (ΔT ÷ 50)^n | 0.515 |
| ΔT | Factor | Output |
|---|---|---|
| 20 K | 0.304 | 608 W |
| 25 K | 0.406 | 812 W |
| 30 K | 0.515 | 1,030 W |
| 35 K | 0.629 | 1,258 W |
| 40 K | 0.748 | 1,496 W |
| 45 K | 0.872 | 1,744 W |
| 50 K | 1 | 2,000 W |
| 55 K | 1.132 | 2,264 W |
| 60 K | 1.267 | 2,535 W |
Show the working
- Correction factor: (30 ÷ 50)^1.3 = 0.515
- Output at ΔT30: 2,000 W × 0.515 = 1,030 W
How it works
- Correction factor = (ΔT ÷ 50)^n, where ΔT = mean water temperature − room temperature and n is the radiator exponent
- Output at your ΔT = ΔT50 output × correction factor
- ΔT50 output = output at your ΔT ÷ correction factor
Our exponent n is a typical figure; use the maker's own n or their correction table where they give one.
Our default (adjustable)
These are typical planning figures and our own allowances, not facts about your product. Change any of them in the calculator to match your bag, pack or tin.
| Figure | Our default (adjustable) | Kind | Source |
|---|---|---|---|
| Radiator exponent n | 1.3 | Our assumption Not yet checked against the source | Our choice: change it to suit your job Radiator exponent n, default 1.3 as stated in brief v2 H2 ("typical from makers"). Stored as an assumption until the Researcher cites a maker's data sheet (e.g. Stelrad, Zehnder) and switches it to typical. |
Regulations and standards
- BS EN 442 (radiator outputs rated at ΔT50)
Explained: BS EN 442 (radiators).
Our checks use the guidance for England unless a badge says otherwise. Wales, Scotland and Northern Ireland have their own rules: check the source for where you live.