Why does the size of the gap decide which product to buy, not just how much?

Because this seal has to work on a joint that opens and shuts thousands of times, and every profile only seals across a narrow band of gap widths. Too little compression and it never touches at all; too much and the door will not latch, or it latches by crushing the strip flat. That flattening is the failure mode worth knowing about — it is called compression set, and it means a strip can be perfectly present, visibly intact, and no longer sealing anything, because it stopped springing back some winters ago. So the useful measurement before ordering is not just the perimeter but the actual gap, taken at the top, at the latch and at the hinge, because a door that has dropped will show three different numbers. It is the one quantity on this page that a permanent sealant never has to worry about, since a caulked joint is not asked to move.

Why does this use the full perimeter, unlike casing which skips the door's bottom?

Air sealing needs to close off the whole gap around the opening, including the threshold (typically with a door sweep) — the goal is different from casing, which is purely cosmetic trim.

Do different weatherstripping types (foam, V-strip, felt) use different amounts?

The linear footage needed is the same regardless of type, since it's based on the opening's perimeter — but door sweeps and thresholds are usually sold separately by width, not by the roll length used for the sides and top.

How do I know if my weatherstripping needs replacing?

Common signs are visible daylight around a closed door, a noticeable draft, or a dollar bill pulling out easily when closed in the door — worn, cracked, or compressed weatherstripping is a common source of household air leakage.

Insulation & Efficiency

Weatherstripping Calculator

Estimate the linear feet or metres of weatherstripping needed to seal door and window openings.

Answers as you typeNo submit button
Every formula citedNamed published standards
Calculated in your browserNo account, nothing uploaded

SettingsSettings for this calculationUS

Market

Imperial · sales tax

Opening Height

The height of the door or window opening.

A standard interior/exterior door is about 80 in (2.03 m) tall.

Opening Width

The width of the door or window opening.

A standard door is about 32-36 in (0.81-0.91 m) wide.

Number of Openings

How many identical openings you're sealing.

For openings of different sizes, run this calculator once per size and add the results.

Stock Roll Length

The length weatherstripping is sold in at your supplier.

10 ft and 17 ft rolls are the common sizes for foam or V-strip weatherstripping in North America; metric markets stock foam and V-strip seal in 5 m and 10 m rolls. Check the length on your specific product before ordering.

Weatherstripping needed

3 x 10 ft rolls

High confidence

Weatherstripping needed (with waste): 20.9 linear ft

Then change the inputs to see how far the answer moves.

Show calculation logic

How this was calculated

Formula source(s)

Weatherstripping seals the full perimeter of an opening (all four sides, since air sealing includes the threshold): length = 2 x (height + width) per opening. Self-adhesive foam and V-strip is stocked in 10 ft and 17 ft rolls in North America and in 5 m and 10 m rolls in metric markets, so the roll count follows the market being read

Inputs used

Opening Height: 6.5 ft
Opening Width: 3 ft
Number of Openings: 1
Stock Roll Length: 10 ft

Intermediate steps

Weatherstripping needed (with waste): 20.9 linear ft

Final result3 x 10 ft rolls

What this calculation does not cover

Gap width is not part of this. The perimeter comes out the same whether the door closes on a hairline gap or one you can see daylight through, and gap width is what decides the profile and thickness you buy. Measure it at the head, at the latch and at the hinge, because a door that has dropped will give three different numbers.
Door sweeps and thresholds are not sized here, and neither are kerf-in or screw-on seals, which are sold in door-length pieces rather than on a roll. The count treats the whole opening perimeter as roll material.
Waste is a flat 10 percent on the total, not a cutting plan. It does not model the offcut left when a roll will not yield another full jamb length, corner overlaps or mitred returns, or a job that runs two strips on the same jamb.
Every opening is treated as a plain rectangle of one size. Out-of-square or racked frames, arched and round-top heads, and the extra run at the meeting stile of a pair of doors are all outside the model.
This is a materials take-off, not an air-leakage or energy figure. It does not estimate the infiltration you will remove or what it saves, and it is not a ventilation assessment: tightening a house that has atmospherically vented combustion appliances is work that has to be checked against those appliances.

Estimated cost — your price

Price per 10 ft roll ($)

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Sources checked 2026-09-02 · in the site-wide review of 2026-09-06 · v1.0.1

Regulatory standards & verification citations1

Weatherstripping seals the full perimeter of an opening (all four sides, since air sealing includes the threshold): length = 2 x (height + width) per opening. Self-adhesive foam and V-strip is stocked in 10 ft and 17 ft rolls in North America and in 5 m and 10 m rolls in metric markets, so the roll count follows the market being read

Cite this page

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Now that you have the number

These guides cover the work this quantity is for — the first ones run this calculator inside the section that raises the question.

Draught-Proofing and Secondary Glazing for Sash Windowsuses this calculator
Consent says the sashes stay. What brush seals, an overhaul and secondary glazing each buy, what each costs the window, and the U-value each one reaches.
Draught-Proofing Doors and Windowsuses this calculator
A candle finds the gaps; the merchant needs lengths. Surveying an old house opening by opening, then turning the round into rolls, sweeps, film and tubes.
Hanging a Fire Door to the Gap Tolerances

Called something else where you work? Threshold and door sill — the term in each market, how close the equivalence really is, and the standard that governs it.

Already gone wrong? There is a draught coming from my window

How to calculate weatherstripping in 5 steps

Opening HeightThe height of the door or window opening.
Opening WidthThe width of the door or window opening.
Number of OpeningsHow many identical openings you're sealing.
Stock Roll LengthThe length weatherstripping is sold in at your supplier.
Weatherstripping neededThe tool computes the weatherstripping needed from those figures and shows the formula, its sources, and a confidence rating alongside it.

Weatherstripping needed by opening height

Page defaults, not your figures above.

Opening Height	Weatherstripping needed (x 10 ft rolls)
3 ft	2
4 ft	2
5 ft	2
6 ft	2
7 ft	3
8 ft	3
9 ft	3

Frequently asked questions

Why does the size of the gap decide which product to buy, not just how much?: Because this seal has to work on a joint that opens and shuts thousands of times, and every profile only seals across a narrow band of gap widths. Too little compression and it never touches at all; too much and the door will not latch, or it latches by crushing the strip flat. That flattening is the failure mode worth knowing about — it is called compression set, and it means a strip can be perfectly present, visibly intact, and no longer sealing anything, because it stopped springing back some winters ago. So the useful measurement before ordering is not just the perimeter but the actual gap, taken at the top, at the latch and at the hinge, because a door that has dropped will show three different numbers. It is the one quantity on this page that a permanent sealant never has to worry about, since a caulked joint is not asked to move.
Why does this use the full perimeter, unlike casing which skips the door's bottom?: Air sealing needs to close off the whole gap around the opening, including the threshold (typically with a door sweep) — the goal is different from casing, which is purely cosmetic trim.
Do different weatherstripping types (foam, V-strip, felt) use different amounts?: The linear footage needed is the same regardless of type, since it's based on the opening's perimeter — but door sweeps and thresholds are usually sold separately by width, not by the roll length used for the sides and top.
How do I know if my weatherstripping needs replacing?: Common signs are visible daylight around a closed door, a noticeable draft, or a dollar bill pulling out easily when closed in the door — worn, cracked, or compressed weatherstripping is a common source of household air leakage.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.