Find Your Ideal Stove Size Today
Use our free stove heat output calculator below to discover the recommended kW output for your room. Once calculated, we’ll show you suitable stoves that match your space and heating needs.
Our stove sizing recommendations are based on standard room volume calculations commonly used across the heating industry, combined with insulation adjustments for more accurate results.
What size stove do you need?
Find the right kW output for your room in under a minute. Tell us your dimensions, adjust for insulation, and we'll match you to suitable stoves from across our range.
A boiler stove typically supplies around 1.5 kW per radiator, plus 3 kW for hot water and a portion of the output to heat the room itself.
Outdoor and glamping stoves are typically smaller (2–5 kW), with a focus on portability, low clearance, and rapid heat-up.
How the calculation works
The starting point is your room volume — length × width × height in metres. We divide that by 14, the long-standing UK rule of thumb for a typically insulated home aiming for 21°C indoors when it's 0°C outside.
That formula alone is a starting point, not a finishing line. A draughty Victorian terrace with single glazing and four exposed walls needs noticeably more output than a new-build with the same volume. The adjustments above account for those differences, which is why the calculator gives you a range rather than a single number.
For unusual rooms — boats, conservatories, listed buildings, very high ceilings — the maths only takes you so far. Speak to our experts →
Common questions
What if my room measurement falls between two sizes?
If your calculation lands between, say, a 4 kW and a 5 kW stove, lean towards the lower end. Stoves are designed to operate at 70–80% of their maximum rated output for clean, efficient burning. An oversized stove run on a low setting will smoulder, glaze the glass, and tar the flue over time.
Should I oversize my stove "just in case"?
It's a common instinct, but no — oversizing is one of the most common stove buying mistakes. A 10 kW stove in a room that needs 5 kW will be too hot at full burn, so you'll run it slowly. Slow burning produces more smoke, more soot, and more creosote in the flue. It also wastes fuel. Buy the right size and you'll burn less wood while staying warmer.
How do I size a stove for an open-plan room?
Treat the connected space as part of the same room when calculating volume — but only the area the heat will actually reach. A kitchen-diner with a wide archway shares heat readily; a hallway or staircase pulls warmth away without holding it. The "open to other rooms" setting in the calculator builds this in.
What if I want to heat radiators too?
Switch to the Boiler stove tab above. A boiler stove provides hot water to your central heating system as well as direct room heat. Sizing depends on the number of radiators, whether you want hot water, and how much output you want left over to heat the stove's own room.
Does the calculator account for DEFRA / smoke control areas?
Yes. After the calculator gives you a kW range, you can filter the matched stoves to show only DEFRA-approved models. If you live in a UK smoke control area — which covers most cities and large towns — DEFRA approval is a legal requirement for burning wood.
Can I use this for a wood-burning cooker or range?
The room-heating calculation applies to wood-burning cookers as well. However, range cookers also produce significant heat through cooking, and many sit in kitchens with extraction. We'd recommend speaking to our team for an accurate sizing, particularly if the cooker will be your primary heat source.
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