How to Use the Weatherstripping Length Calculator
Most winter drafts and summer cooling loss creep in through tiny gaps around windows and exterior doors. Before you start sealing, knowing exactly how much weatherstripping to buy saves you an extra trip to the hardware store.
The math is simple: the perimeter of one window or door is (width + height) × 2, multiplied by how many units you're sealing. We then add a 10% buffer to cover corner trimming and any strip that fails to stick.
Weatherstripping typically comes in 10, 20, or 30-foot rolls, so dividing your total length by the roll size (rounded up) tells you exactly how many rolls to buy. Consider whether V-strip, foam tape, or door sweeps suit your frame material best.
Frequently Asked Questions
Drafts usually leak in along the whole perimeter where the frame meets the sash or door, so sealing the entire width and height is most effective. Pay extra attention to the latch side and the bottom threshold, where gaps tend to be largest.
The buffer accounts for corner trimming, overlaps, and any strip that fails to stick and needs replacing. Since rolls come in fixed lengths, buying the exact measured amount often leaves you short.