Determine the ideal heat output for your radiators. Input room dimensions, insulation quality, and window types to calculate the BTU or wattage needed. Prevents inefficient overheating or inadequate warmth.
Open Radiator Size Estimator → free, no sign-inFitting a radiator that's too small leaves a room permanently cold. Fitting one that's too large wastes energy and money. Getting it right means calculating the heat output needed based on room dimensions, ceiling height, insulation quality, and window type — a calculation that's straightforward in principle but tedious to do manually. The Radiator Size Estimator does it for you: enter the room details and get the recommended BTU or wattage output immediately.
Anyone planning a home renovation, replacing an old radiator, or trying to understand why a particular room never gets warm will find this genuinely useful. It removes the guesswork from a purchase most people only make once every decade.
No tutorials. No learning curve. Open it and get started.
No server uploads. Results are given in both BTU and watts, so you can match them directly against the output specifications on any radiator you're considering.
Completely free. No trial period. No premium tier for basic functionality. No account required. Use it as often as you need.
One job, done well. Radiator Size Estimator was built to solve a specific problem cleanly. No feature bloat, no ads, no distractions.
What inputs do I need?
Room dimensions (length, width, height), insulation type, and window type.
Does it calculate in BTU or watts?
Both — results are given in BTU and watts.
Is this accurate enough to buy a radiator?
Yes — it provides a solid estimate for standard residential rooms. Always allow a 10-15% margin.
Does it account for different room types (conservatory, bathroom, etc.)?
Yes — different room types have different heat loss factors accounted for.
Is this free?
Yes — completely free.
Free. Instant. No sign-in. Open it and get the job done.
Open Radiator Size Estimator on Doathingy.com →