Room Heater BTU Calculator

RadiatorBTU Sizer - professional calculator.

Not sure how many BTUs you need to heat a room? Buying the wrong radiator wastes money and leaves you cold. This calculator determines the exact heating output required for any room based on its dimensions, insulation quality, window area, and climate zone.

Enter room length, width, ceiling height, insulation level, window area, and climate zone. Get required BTU output, recommended radiator sections, and kW equivalent instantly.

WHAT IT CALCULATES:

• Required BTU/h for the room
• Heat loss through walls, windows, and ceiling
• Number of radiator sections needed
• Output in BTU and kW
• Insulation and exposure adjustments

KEY FEATURES:

• Multiple climate zone presets
• Insulation quality levels (poor to excellent)
• Window type adjustments
• Baseboard and panel radiator support
• Works completely offline
• No account or login required

Built for HVAC technicians, plumbers, heating contractors, and homeowners planning system upgrades.