Example 1
- Volume: 50 m³
- Heat demand: 40 W/m³
Heating power: 2000 W
That is about 2.00 kW
This is a straightforward example of moving from volume to an approximate heating power value.
Heating calculator
Type room volume in m³ and a W/m³ figure. The calculator multiplies them to watts and shows kilowatts. A 50 m³ room at 40 W/m³ is 2000 W, about 2.00 kW. An 84 m³ living room at 35 W/m³ is 2940 W. A 27.3 m³ bedroom at 45 W/m³ is 1228.5 W, about 1.23 kW.
This calculator gives a fast, approximate heating power result based on room volume and an assumed W/m³ demand value. It is useful for first comparisons, but it does not replace a full heat-loss calculation. Related: room volume, insulation requirement.
Results
Room volume (m³), Heat demand (W/m³), Building standard (auto W/m³) and Room type. The result shows up here.
How the results are calculated
The heating calculator sketches power from volume. The formula is m³ times W/m³, and kW is watts divided by 1000. Room type and window area refine the result only when you fill them. Building standard can supply the figure when you leave W/m³ empty.
A 50 m³ room at 40 W/m³ is 2000 W, two kilowatts for an ordinary living room. A taller 84 m³ salon at 35 W/m³, a warmer standard, is 2940 W. A small 27.3 m³ bedroom at 45 W/m³ is 1228.5 W. Those three volumes come from the volume card: 5×4×2.5, 6×5×2.8, and 3.5×3×2.6 m.
Type room volume and heat demand in W/m³, or pick a building standard. Leave room type and windows empty when the plain product is enough. A comma in 27.3 works the same as 27,3.
The 50 m³ volume lives on the room volume calculator. Insulation for 120 m² at 60×120 cm and 8% is 181 boards and R about 4.17, another calculator. Paint does not turn into watts.
This is a sketch, not a design heat loss. An older house sits nearer 45-50 W/m³, a newer one nearer 30-35. Empty windows add nothing. Type 50 and 40, click Calculate, and match 2000 W and 2.00 kW.
Then 84 and 35: 2940 W. 27.3 and 45: 1228.5 W, the third card.
How to use this calculator
- Type volume in m³, for example 50 from a 5×4×2.5 m room.
- Enter heat demand in W/m³, for example 40, or pick a building standard.
- Leave room type and window area empty when the plain product is enough.
- Click Calculate. 50 m³ and 40 W/m³ give 2000 W, about 2.00 kW.
- Volume belongs on the room volume page. This calculator stays watts.
kW from 50 m³ at 40 W/m³
Volume times the W/m³ figure. A 50 m³ room at 40 W/m³ is 2000 W, about 2.00 kW.
- kW
- Power in kilowatts next to watts. 2000 W is 2.00 kW. An 84 m³ living room at 35 W/m³ is 2940 W, about 2.94 kW.
- W/m³
- The demand field. 40 on 50 m³ is 2000 W. 45 on a 27.3 m³ bedroom is 1228.5 W, about 1.23 kW.
- m³
- Room volume from the volume card. 50 m³ at 40 W/m³ is that 2.00 kW, not floor area alone.
Example scenarios
Example 2
- Volume: 84 m³
- Heat demand: 35 W/m³
Heating power: 2940 W
That is about 2.94 kW
A lower W/m³ demand can offset a larger room volume if the building standard is better.
Example 3
- Volume: 27.3 m³
- Heat demand: 45 W/m³
Heating power: 1228.5 W
That is about 1.23 kW
A smaller room does not always mean very low heating power if the assumed demand value is higher.
Related calculators
FAQ
How many watts at 50 m³ and 40 W/m³?
2000 W, about 2.00 kW. That is the first card example.
How many watts at 84 m³ and 35 W/m³?
2940 W, about 2.94 kW. A 6×5×2.8 m living room from volume.
How many watts at 27.3 m³ and 45 W/m³?
1228.5 W, about 1.23 kW. A small bedroom, a higher figure.
Where do I get 50 m³?
From room volume: 5×4×2.5 m = 50. Walls and paint are other cards.
Do empty windows change the 2000 W?
No. Windows and room type enter only when you fill them.
Which W/m³ should I pick?
A sketch of 40 for an ordinary room. An older building sits nearer 45-50, a newer one 30-35. Standard can fill the number for you.
Does 2.00 kW replace a heating design?
It is the product of two fields. Heat loss, bridges, and ventilation stay off the calculator.
How do 181 insulation boards change these watts?
Not on this page. Insulation counts boards and R. Here it stays W = m³ × W/m³.
Does a comma in 27.3 m³ work?
Yes. 27.3 and 27,3 are the same volume. At 45 W/m³ you get 1228.5 W.
How many kW at 100 m³ and 40 W/m³?
4000 W, which is 4.00 kW. The formula is linear: volume times the W/m³ sketch.
Knowledge sources
Volume and waste come from the sizes you type. Below are volume and NIST SI units.
Page updated in 2026.