What Size Log Burner Do I Need?

By Burner Hub  ·  April 2026  ·  8 min read

Choosing the wrong size stove is one of the most common, and costly, mistakes buyers make. Too small and you'll run it flat out trying to heat the room, straining the firebox and burning through fuel. Too large and you'll be forced to "slumber" it by restricting the air supply, which causes tar and creosote to build up inside the flue liner. That's a fire risk and an expensive fix.

This guide walks you through the exact calculation, adjustments for insulation, and the additional factors, open-plan rooms, staircases, large windows, that can shift your answer by 1-2kW. There's a free interactive calculator below, and we've matched each kW range to specific stoves available from Burner Hub with standard UK delivery (£100) available to all UK addresses.

Step 1: Measure Your Room's Volume

You need three measurements in metres:

• Length of the room
• Width of the room
• Height from floor to ceiling, standard UK ceiling is 2.4m, but always measure

Multiply them: Length × Width × Height = cubic metres (m³). A room that is 5m × 4m × 2.4m = 48m³.

Step 2: Divide by 14, Then Adjust for Insulation

The standard rule is 1kW of heat output per 14 cubic metres of well-insulated space. But your home's insulation level changes this significantly:

Using the same 48m³ room:

• Poorly insulated: 48 ÷ 10 = 4.8kW → choose a 5kW stove
• Average insulation: 48 ÷ 14 = 3.4kW → choose a 4kW or 5kW stove
• Well insulated: 48 ÷ 20 = 2.4kW → a 3kW or 4kW stove is sufficient

Quick-Reference kW Table

Use this to match your kW figure to the right stove type, then browse the relevant collection at Burner Hub.

Recommended Stoves by Room Size

Every stove below is in stock at Burner Hub Click through to see full specifications and pricing.

Smaller Rooms, Up to 4.6kW

If your calculation gives 3-4kW, a compact multi-fuel stove is the smart choice. The Muckross 4.6kW from Henley is one of their best-selling models for smaller spaces, Ecodesign ready and efficient.

Standard Living Rooms, 5kW

A 5kW stove is right for the vast majority of UK homes. It's also the threshold below which no additional air vent is required under building regulations, making installation simpler and cheaper. Browse all 5kW options in our wood burning stoves collection.

Large Rooms and Open-Plan, 7kW+

Rooms over 80m³, spaces with open staircases, or older pre-1950 homes with poor insulation typically need 7kW or more. A multi-fuel stove is strongly worth considering at this output, it burns both wood and smokeless fuel, which matters if your address falls within an Essex Smoke Control Area.

For whole-home heating or rooms over 140m³, a boiler stove is the most efficient solution. The Henley Sherwood 12 Eco Boiler Multi Fuel Stove delivers powerful output for both room and central heating. Contact our team for a free consultation on whether a boiler stove suits your property.

Unsure whether to choose wood-burning or multi-fuel? See our detailed guide: Multi Fuel vs Wood Burning Stove: The Complete Guide.

Factors That Change Your Calculation

The cubic volume formula is your baseline, but the following can push your requirement up by 1-2kW:

Open-Plan Rooms

If your room connects to another through a wide archway with no door, measure both areas as one combined volume. Heat doesn't respect walls it can't see.

Open Staircases

Heat rises. An open staircase in your room means warm air drifts upstairs. Add at least 1-1.5kW to your calculation, or go up to the next stove size.

Large Windows or Single Glazing

Single-glazed windows and large patio doors are significant heat sinks. If your room has substantial glass, especially on north or east-facing walls, treat the insulation as "poor" and divide by 10.

High or Vaulted Ceilings

Many Victorian properties have ceilings of 2.7m, 3m, or higher. Always measure your actual ceiling height. A 3m ceiling in a 5m × 4m room adds 18% more volume, enough to push you from a 5kW to a 6kW stove.

The 5kW Ventilation Rule

Under UK building regulations, any stove with a nominal output above 5kW requires a permanently open air vent in the same room. If your calculation gives 5.5kW but a 5kW stove would nearly cover it, staying below 5kW avoids the cost and complexity of a vent. Ask our team for advice if you're on the borderline.

Nominal vs Maximum Output: Which Number to Use

Every stove spec sheet shows two heat output figures:

• Nominal output, the kW produced when running efficiently at its design point. This is the number to match against your room calculation.
• Maximum output, the peak achievable with a full load and wide-open air. Stoves should not be run at maximum for extended periods.

Always size to the nominal output. Running a stove below its nominal (because you bought too large) is called "slumbering", it causes tar to condense in the flue liner, which is a fire risk over time. All stoves in Burner Hub's range clearly display both figures alongside efficiency ratings on their product pages.

No Chimney? Your Options

No chimney or traditional flue doesn't mean no stove. You have three good options:

• Twin-wall flue system: A modern twin-wall flue can be routed through a wall or ceiling in almost any property, opening up the full range of wood burning and multi-fuel stoves. We stock complete Specflue liner kits, browse our accessories range or ask us for a flue recommendation.
• Bioethanol stoves: No flue, no chimney, no installation. Our bioethanol stoves from Henley produce a real flame from clean-burning ethanol fuel, ideal for flats, rental properties, and rooms where a flue isn't practical.
• Electric stoves: Our electric stoves and media wall fires need only a standard 13A socket. No installation, no sizing calculation, heat is controlled by thermostat.

Frequently Asked Questions

Summary: How to Size Your Log Burner

1. Measure your room: length × width × height in metres
2. Divide by 14 (average), 10 (poorly insulated), or 20-25 (modern build)
3. Round up to the nearest available stove size
4. Add 1-2kW for open staircases, large single-glazed windows, or high ceilings
5. If output is above 5kW, factor in the cost of a room air vent
6. In an Essex Smoke Control Area? Choose a DEFRA Approved stove

Browse the full Burner Hub range, wood burning stoves, multi-fuel stoves, electric stoves, and bioethanol stoves, all available to order online with UK delivery. Or get in touch for a free, no-obligation installation quote from our Essex-based team.