Radiator Calculator Pro
Heat Output & BTU Calculator
Free · In‑App Purchases · Designed for iPad. Not verified for macOS.
Room-by-room radiator sizing with ΔT correction for heat pumps. Watts, BTU/h, metric or imperial. Free for one room; PRO unlocks unlimited rooms.
Room-by-room radiator sizing. Watts and BTU/h output for any room, factoring volume, glazing, external walls, roof and floor exposure, and insulation standard.
Calculation
Heat output per room with adjustments for:
• Room type (8 presets: bedroom, living room, bathroom, kitchen, hallway, office, conservatory, garage)
• Internal volume
• Window-to-floor ratio
• Number of external walls (0–4)
• What's above (loft, pitched roof, flat roof, heated space)
• What's below (garage, unheated cellar, uninsulated floor, heated floor)
• Insulation level: poor (older single-glazed) → average (modern build) → good → excellent (new-build, triple-glazed)
• Mean water temperature - ΔT30, ΔT35, ΔT40, ΔT50, ΔT60
ΔT correction uses the standard panel-radiator exponent (n = 1.30) per EN 442 testing convention. A 5% safety margin is applied to avoid undersizing.
Heat-pump systems
Select ΔT35 or ΔT30 to spec radiators for low-temperature systems. Output is rescaled — a 1000W ΔT50-rated radiator delivers ~630W at ΔT35 — so you size to actual delivered heat, not nameplate.
Output
• Watts and BTU/h side-by-side
• Metric or imperial dimensions
• Whole-home heat-loss total
• Share or export room specs as text
For plumbers, heating engineers, and heat-pump installers sizing radiator schedules, and homeowners or landlords running their own jobs.
Ratings & Reviews
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Thank you for using Radiator Calculator PRO. We’re always improving the app with performance enhancements, bug fixes, and tweaks to make the experience even better for you.
The developer, DigitalKind Ltd, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- DigitalKind Ltd
- Size
- 15.7 MB
- Category
- Utilities
- Compatibility
Requires iOS 26.0 or later.
- iPhone
Requires iOS 26.0 or later. - iPad
Requires iPadOS 26.0 or later. - Mac
Requires macOS 26.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 26.0 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- In-App Purchases
Yes
- Radiator Calculator PRO $3.99
- Copyright
- © 2025 DigitalKind