How to convert BTU to Watts

It is often useful to convert BTU to watts to compare specs and size correctly. Radiators are often listed in BTU's, while boilers and electric heating often use Watts. Be sure when comparing to keep comparisons at the same Delta T rating. For an explanation of Delta T ratings and how to standardise in order to compare like for like use the Delta T (ΔT) conversion button below. Please note all the outputs listed on the Trade Radiators website is at the UK standard, ΔT50. If you are needing to find the radiator output required to heat a given room, click open BTU Calculator.

Open BTU Calculator Delta T Conversion Shop Vertical Radiators Shop Column Radiators

Radiator sizing in three steps

1. Open BTU Calculator

   Calculate each room’s required output (BTU/hr at ΔT50).

2. Convert Units (BTU ↔ Watts)

   Match product specs to your unit. Unit conversion doesn’t change ΔT.

3. Align ΔT (Delta T Conversion)

   If a spec is ΔT60, adjust to ΔT50 (×0.79) before comparing. Choose the next size up if you’re between outputs.

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Quick Reference: BTU ↔ Watts

BTU → Watts (ΔT‑independent)

BTU	Watts
1,000	293
1,500	440
2,000	586
2,500	733
3,000	879
3,500	1,026
4,000	1,172
4,500	1,319
5,000	1,465
5,500	1,612
6,000	1,758
6,500	1,905
7,000	2,051
7,500	2,198
8,000	2,345
8,500	2,491
9,000	2,638
9,500	2,784
10,000	2,931
10,500	3,077
11,000	3,224
11,500	3,370
12,000	3,517
12,500	3,663
13,000	3,810
13,500	3,956
14,000	4,103
14,500	4,250
15,000	4,396
15,500	4,543
16,000	4,689
16,500	4,836
17,000	4,982
17,500	5,129
18,000	5,275
18,500	5,422
19,000	5,568
19,500	5,715
20,000	5,861

Rounded to nearest whole watt using 1 BTU = 0.29307107 W.

Watts → BTU (ΔT‑independent)

Watts	BTU
100	341
200	682
300	1,024
400	1,365
500	1,706
600	2,047
700	2,388
800	2,730
900	3,071
1,000	3,412
1,100	3,753
1,200	4,095
1,300	4,436
1,400	4,777
1,500	5,118
1,600	5,459
1,700	5,801
1,800	6,142
1,900	6,483
2,000	6,824
2,100	7,165
2,200	7,507
2,300	7,848
2,400	8,189
2,500	8,530
2,600	8,872
2,700	9,213
2,800	9,554
2,900	9,895
3,000	10,236

Rounded to nearest whole BTU using 1 W = 3.412141633 BTU.