Example 1
- Length: 5 m
- Width: 4 m
- Height: 2.5 m
Volume: 50 m³
This is a classic example of a residential room with a typical ceiling height.
Room volume calculator
Type length, width, and height. The calculator multiplies the three sides, subtracts a void, and multiplies by repeats. A 5 by 4 by 2.5 m room is 50 m³. A 6 by 5 by 2.8 m living room is 84 m³.
Room volume is how much space is inside - handy for air changes, heating load, and comparing rooms with the same floor area but different ceiling heights. Next: heating power, wall area.
Results
Length, width, height, and a deduction. Room volume shows up here.
How the results are calculated
Room volume counts cubic meters. The formula is max(0, length times width times height minus deducted volume) times the repeat count. Suggested heat is about 40 W/m³, times a room-type factor: bathroom 1.2, attic 1.1. That is a sketch, not an energy audit.
A 5 by 4 by 2.5 m living room is 50 m³. At 40 W/m³ the heating page next door shows 2000 W, 2.00 kW. A 6 by 5 by 2.8 m salon is 84 m³; at 35 W/m³ that is 2940 W. A 3.5 by 3 by 2.6 m bedroom is 27.3 m³, about 1.23 kW at 45 W/m³.
Type length, width, and height in the header unit. Deduct volume, room type, and repeats only when you need them. An empty deduction subtracts nothing. Two matching rooms go in as repeat count 2, instead of adding sides by hand.
Heating watts from this volume live on the heating calculator. Walls 4 by 3 by 2.6 m are 36.4 m² of paint, a different formula. Floor area 5 by 4 m is 20 m², with no height.
Height 2.5 m on the same 20 m² floor is 50 m³; 2.8 m would be 56 m³. An attic rake is not in the box: type a mean height or deduct dead volume. Bathroom type only lifts the watt sketch, not the volume itself.
Type 5, 4, and 2.5, click Calculate, and match 50 m³. Then 6, 5, and 2.8: 84 m³, the second card.
How to use this calculator
- Type length, width, and height in the header unit, for example 5, 4, and 2.5.
- Optionally deduct volume in m³, for example a closet you do not heat.
- Leave room type and repeat count empty when you have one ordinary room.
- Click Calculate. 5×4×2.5 m is 50 m³. 6×5×2.8 m is 84 m³.
- Watts belong on the heating page from this volume. This calculator stays m³.
m³ from three sides
Room volume: 5×4×2.5 m is 50 m³. A 6×5×2.8 m living room is 84 m³. A 3.5×3×2.6 m bedroom is 27.3 m³.
- m³
- Volume. 50 from a 5×4×2.5 m room. 84 from the living room. Paste it into W/m³ on heating.
- W
- Power sketch. 50 m³ × 40 W/m³ = 2000 W. Bathroom type only scales that sketch.
Example scenarios
Example 2
- Length: 6 m
- Width: 5 m
- Height: 2.8 m
Volume: 84 m³
With a higher ceiling, floor area alone is no longer enough to fully compare interiors.
Example 3
- Length: 3.5 m
- Width: 3 m
- Height: 2.6 m
Volume: 27.3 m³
This is a good example of how a small room can have a noticeably different usable volume than floor area alone might suggest.
Example 4
- 2.4 × 1.6 × 2.5 m
9.60 m³
How many m³ is a 2.4×1.6×2.5 m bathroom? 9.60 m³.
Example 5
- 3.8 × 3.2 × 2.6 m
31.62 m³
How many m³ is a 3.8×3.2×2.6 m kitchen? 31.62 m³.
Example 6
- 6.5 × 4.2 × 2.7 m
73.71 m³
How many m³ is a 6.5×4.2×2.7 m living room? 73.71 m³.
Example 7
- 7.2 × 1.15 × 2.5 m
20.70 m³
How many m³ is a 7.2×1.15×2.5 m hallway? 20.70 m³.
Example 8
- 3.5 × 3 × 2.6 m
- repeat 2
54.60 m³
How many m³ are two matching 3.5×3×2.6 m bedrooms? 54.60 m³.
Related calculators
FAQ
How many m³ is a 5×4×2.5 m room?
Volume is 50 m³, because 5×4×2.5 = 50. At 40 W/m³ that is 2000 W on the heating page.
How many m³ is a 6×5×2.8 m living room?
You get 84 m³. At 35 W/m³ that is 2940 W, about 2.94 kW. Same product of three sides.
How many m³ is a 3.5×3×2.6 m bedroom?
You get 27.3 m³. At 45 W/m³ that is 1228.5 W, about 1.23 kW. Paste that into heating power.
How is volume different from floor area?
A 5 by 4 m floor is 20 m². Volume multiplies that by height. At 2.5 m you get 50 m³.
Why a bathroom or attic type?
The watt sketch multiplies 40 W/m³ by 1.2 or 1.1. Volume itself stays the product of the three sides.
How do I count two matching rooms?
Type one room and set repeats to 2. Or add volumes on paper and leave one room here.
Is a roof rake inside the 50 m³?
The formula uses a box. Type a mean height, or deduct dead volume.
Where do I get 2000 W from 50 m³?
On the heating calculator: 50 × 40 = 2000 W. Wall insulation is a separate board-count card.
Does an empty deduction zero the volume?
An empty deduction subtracts nothing. A typed zero also leaves the full product of the three sides.
How many m³ at 3×5×4 m minus 2.7 m³?
57.3 m³ from 60 minus 2.7, before repeats. The product 3×5×4 = 60, then the deduction.
Knowledge sources
Volume and waste come from the sizes you type. Below are volume and NIST SI units.
Page updated in 2026.