Stove Size Calculator
Enter your room length, width and ceiling height and how well insulated it is. The calculator works out the heat output you need in kW and BTU an hour, a stove size to look for and whether you need an air vent.
- Stove kW
- BTU an hour
- Air vent
Measure the room the stove will heat. Open plan spaces count as one room.
A common rule is one kW for every 14 cubic metres of room. A 5 × 4 m room with a 2.4 m ceiling is 48 m³, so it needs about 3.4 kW, a 4 kW stove. A poorly insulated room needs more and a new, well insulated one less. Stoves over 5 kW usually need a permanent air vent.
Stove size chart
Average insulation, 2.4 m ceiling. Search for a room.
| Room (m) | Volume (m³) | Output (kW) | Stove |
|---|---|---|---|
| 3 × 3 | 21.6 | 1.5 | 4 |
| 4 × 3 | 28.8 | 2.1 | 4 |
| 4 × 4 | 38.4 | 2.7 | 4 |
| 5 × 4 | 48 | 3.4 | 4 |
| 6 × 4 | 57.6 | 4.1 | 5 |
| 6 × 5 | 72 | 5.1 | 6 |
| 8 × 5 | 96 | 6.9 | 7 |
| 10 × 6 | 144 | 10.3 | 12 |
kW = volume ÷ 14.
Room volume and output
Average insulation. Slide the room volume.
The room is drawn with its stove and the output it needs.
How to size a stove
Room to kW. Step through it.
Measure
L × W × H.
Choose a clean-burning, low-emission stove. Burn only dry wood with under 20% moisture.
Wood, multi-fuel or boiler stove
Stove types. Compare them.
Logs only.
Wood or smokeless.
Heats water.
Boiler stoves heat water and radiators too, so they need sizing for the whole house.
Before you buy
Stove checks. Tick each item.
Tick each item as you go.
Fit a carbon monoxide alarm in every room with a stove.
What you get
Stove sizing. Each tile explains one result.
kW.
An hour.
Size.
If needed.
Room.
One kW is about 3,412 BTU an hour.
Frequently Asked Questions
No question matches that search.
What size stove do I need?
Divide the room volume in cubic metres by about fourteen for average insulation.
Is a bigger stove better?
No. An oversized stove is run turned down, which burns dirty and wastes fuel.
Does a five kilowatt stove need a vent?
Usually not in the UK. Stoves over five kilowatts need a permanent air vent.
How do I convert kW to BTU?
Multiply by three thousand four hundred and twelve.
Does insulation change the size?
Yes. A well insulated room needs much less heat.
Can one stove heat a whole house?
Only an open-plan or very well insulated one, or with a boiler stove.
What wood should I burn?
Dry, seasoned wood with less than twenty per cent moisture.
Warmth without waste
Match the stove to the room, burn dry wood and enjoy steady, clean heat.
More size calculators
Each one has its own calculator, worked examples and answers to common questions.