Calculate Your BTU Requirement
Enter your room details below to find the exact radiator output you need.
Your Radiator BTU Result
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Where to Buy Radiators
Compare radiator prices at these UK retailers before you buy — prices vary significantly between suppliers.
| Retailer | Best For | Why We Recommend |
|---|---|---|
| BestHeating | Panel & column radiators, designer styles | UK's largest radiator specialist — huge range, competitive prices |
| Screwfix | Trade-grade panel radiators, same-day collection | Best for tradespeople — collect from 900+ stores nationwide |
| Victorian Plumbing | Designer & statement radiators | Best designer radiator range in the UK, good sale prices |
Links help support this free tool. Always compare prices before buying.
Typical BTU Requirements by Room Size (2026)
Use this table as a quick reference guide — these figures assume average insulation and double glazing.
| Room Size | Room Type | Estimated BTU | Estimated kW |
|---|---|---|---|
| 10 m² | Bedroom | 2,500 – 3,500 BTU | 0.7 – 1.0 kW |
| 15 m² | Living Room | 4,500 – 6,000 BTU | 1.3 – 1.8 kW |
| 20 m² | Living Room | 6,000 – 8,000 BTU | 1.8 – 2.3 kW |
| 8 m² | Bathroom | 2,000 – 3,000 BTU | 0.6 – 0.9 kW |
| 12 m² | Kitchen | 3,000 – 4,500 BTU | 0.9 – 1.3 kW |
Cost of New Radiators — UK Prices (2026)
| Radiator Type | Supply Only | Installed (inc. labour) |
|---|---|---|
| Single Panel (600×1000mm) | £80 – £150 | £250 – £400 |
| Double Panel (600×1200mm) | £120 – £250 | £300 – £500 |
| Column Radiator (Large) | £250 – £500 | £450 – £750 |
| Designer Radiator | £300 – £800+ | £500 – £1,100+ |
Note: Labour typically costs £150–£300 per radiator for a like-for-like replacement. New pipework increases this significantly. Always get a fixed quote from a qualified plumber.
How to Accurately Measure Your Room for a BTU Calculation
Step 1: Measure Room Dimensions
Use a tape measure to find the length and width of the room in metres. For non-rectangular rooms, break the space into rectangular sections and add the areas together. Measure the ceiling height from floor to ceiling — the standard UK ceiling is 2.4m.
Step 2: Assess Your Insulation
"Poor" means solid brick walls with no cavity. "Average" is cavity walls with no fill. "Good" means standard cavity wall insulation. "Excellent" means modern high-spec insulation (typically post-2000 builds).
Step 3: Count External Walls & Windows
An external wall borders the outside of the property — not a shared wall with a neighbour. Count how many external walls your room has. Then identify whether the windows are single, double, or triple glazed.
Step 4: Identify Room Features
Note the floor level (ground floor loses more heat through the floor) and use a compass app on your phone to check if any external walls face north. North-facing rooms need around 15% more heating capacity.
Step 5: Enter & Calculate
Enter all values into the calculator above to get your precise BTU requirement. If replacing a heat pump Paint Patio Garden Room Pergola, note that heat pumps run at lower flow temperatures — you may need larger radiators.