Draught-Proofing Calculator \u2014 Materials & Savings Estimate
Calculate draught-proofing strip, chimney balloons and letterbox covers needed for your home. Estimate annual energy savings.
Doors & Windows
Front, back, side doors
Sliding sash windows
Hinged opening windows
Other Draught Sources
Chimneys not in use
Strip Roll Size & Pricing (optional)
How We Calculate This
This calculator estimates the draught-proofing materials you need by calculating the total perimeter of doors, windows and other openings that need sealing, then working out how many rolls of draught strip to buy.
Perimeter estimates used
- External door: ~6.0m perimeter (including threshold)
- Sash window: ~6.5m (two sashes, each with sealing perimeter)
- Casement window: ~4.0m perimeter (typical opening casement)
- Loft hatch: ~3.6m perimeter
Additional products
- Chimney balloon/sheep: One per unused chimney to prevent heat escaping
- Letterbox cover: A brush-type internal cover to reduce draughts through the letterbox
Energy savings
Savings estimates are based on Energy Saving Trust data for typical UK homes. Draught-proofing costs relatively little but can make a noticeable difference to comfort and heating bills. It complements other insulation measures and is often recommended as a first step in improving home energy efficiency.
Frequently Asked Questions
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Last updated: February 2026
All calculations are estimates. Verify with your supplier.