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Watts per square metre to BTU per hour square foot

1 watt per square metre = 0.317 BTU per hour square foot · 1 BTU/(h·ft²) = 3.1546 W/m²

1 watt per square metre = 0.317 BTU per hour square foot

How it’s calculated

BTU/(h·ft²) = W/m² × 0.3169983306

  • Multiply the value in watts per square metre by 0.3169983306.
  • To go back, divide by 0.3169983306 (or multiply by 3.154590745).
  • 1 W/m² = 0.3169983306 BTU/(h·ft²) · 1 BTU/(h·ft²) = 3.154590745 W/m²
Show worked solutionFactor, unit cancellation and rounding, step by step

  1. Find the conversion factor

    By definition 1 BTU/(h·ft²) = 3.15459074506305 W/m². Source: BIPM SI Brochure (9th ed.); NIST SP 811 / Handbook 44.

  2. Multiply by the factor written as a fraction

    Put W/m² in the denominator so it cancels, leaving BTU/(h·ft²).

  3. Calculate (unrounded)

  4. Round the answer

    Rounded to 5 significant figures.

Answer: 0.317 BTU/(h·ft²)

1 W/m² in other units

Batch convert W/m² → BTU/(h·ft²)
Results
  1. 1 W/m² = 0.317 BTU/(h·ft²)
  2. 5 W/m² = 1.585 BTU/(h·ft²)
  3. 10 W/m² = 3.17 BTU/(h·ft²)
  4. 25 W/m² = 7.925 BTU/(h·ft²)

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Quick examples

  • 1 watt per square metre = 0.317 BTU per hour square foot
  • 5 watts per square metre = 1.585 BTU per hour square foot
  • 10 watts per square metre = 3.17 BTU per hour square foot
  • 25 watts per square metre = 7.925 BTU per hour square foot
  • 100 watts per square metre = 31.7 BTU per hour square foot

About these units

Watt per square metre (W/m²)

SI (metric)

SI unit of heat flux (and irradiance). Solar irradiance at ground ≈ 1 000 W/m².

Base unit

Source: BIPM SI Brochure (9th ed.)

BTU per hour square foot (BTU/(h·ft²))

US & imperial (identical)

IT BTU basis: ≈ 3.154 591 W/m².

1 BTU/(h·ft²) = 3.154590745 W/m²

Source: NIST SP 811 / Handbook 44

Watts per square metre to BTU per hour square foot conversion table

watt per square metre (W/m²) to BTU per hour square foot (BTU/(h·ft²))
Watts per square metre (W/m²)BTU per hour square foot (BTU/(h·ft²))
0.1 W/m²0.0317 BTU/(h·ft²)
0.5 W/m²0.1585 BTU/(h·ft²)
1 W/m²0.317 BTU/(h·ft²)
2 W/m²0.634 BTU/(h·ft²)
3 W/m²0.95099 BTU/(h·ft²)
4 W/m²1.268 BTU/(h·ft²)
5 W/m²1.585 BTU/(h·ft²)
6 W/m²1.902 BTU/(h·ft²)
7 W/m²2.219 BTU/(h·ft²)
8 W/m²2.536 BTU/(h·ft²)
9 W/m²2.853 BTU/(h·ft²)
10 W/m²3.17 BTU/(h·ft²)
15 W/m²4.755 BTU/(h·ft²)
20 W/m²6.34 BTU/(h·ft²)
25 W/m²7.925 BTU/(h·ft²)
30 W/m²9.5099 BTU/(h·ft²)
40 W/m²12.68 BTU/(h·ft²)
50 W/m²15.85 BTU/(h·ft²)
75 W/m²23.775 BTU/(h·ft²)
100 W/m²31.7 BTU/(h·ft²)
250 W/m²79.25 BTU/(h·ft²)
500 W/m²158.5 BTU/(h·ft²)
1,000 W/m²317 BTU/(h·ft²)

Related conversions

Frequently asked questions

How do I convert watts per square metre to BTU per hour square foot?

Use BTU/(h·ft²) = W/m² × 0.3169983306. Multiply the value in watts per square metre by 0.3169983306.

How many BTU per hour square foot are in 1 watt per square metre?

1 watt per square metre (W/m²) equals 0.317 BTU per hour square foot (BTU/(h·ft²)); more precisely 0.3169983306.

How many watts per square metre are in 1 BTU per hour square foot?

1 BTU per hour square foot (BTU/(h·ft²)) equals 3.1546 watts per square metre (W/m²); more precisely 3.154590745.

What is 10 W/m² in BTU/(h·ft²)?

10 watts per square metre = 3.17 BTU per hour square foot.

What is a watt per square metre?

SI unit of heat flux (and irradiance). Solar irradiance at ground ≈ 1 000 W/m².

What is a BTU per hour square foot?

IT BTU basis: ≈ 3.154 591 W/m².

Formula: BTU/(h·ft²) = W/m² × 0.3169983306. Factors last reviewed 2026-10-27.