Weatherstripping Calculator

Calculate weatherstripping length needed, air leakage reduction, and annual energy savings for doors and windows by gap size and strip type

Door / Window Details

Weatherstripping Needed
25.7
linear feet
Perimeter -- ft
With 20% Waste Factor -- ft
Est. Material Cost --
Air Leakage & Energy
Air Infiltration (unsealed) -- CFM
Est. Reduction from Sealing --%
Annual Energy Savings $--
Payback Period -- months

Weatherstripping Types — Comparison

Type Best Location Durability Cost/ft R-Value Improvement Notes
Foam Tape (adhesive)Door top/sides, windows1–3 years$0.15–0.40LowEasy DIY; compresses over time
V-Strip / Tension SealDoor/window sides & top5–10 years$0.30–0.80ModerateBest for side gaps; metal or plastic
Door SweepDoor bottom (interior)3–7 years$0.40–1.20GoodBrushes or vinyl; screws to door face
Door ShoeDoor bottom (threshold)5–15 years$1.50–3.00ExcellentReplaces threshold; best seal
Compression StripDoor stops (all sides)3–7 years$0.50–1.50GoodFoam or rubber; nailed or screwed
Bulb Seal / Kerf SealDoor stop kerf channel5–10 years$0.60–1.80Very GoodRequires kerf cut in door stop
Magnetic (Garage)Garage door perimeter5–10 years$1.00–2.50Very GoodAdheres to metal doors; full seal

Where to Use Each Type

Door Top & Sides

Use V-strip (metal or plastic tension seal) for long-lasting compression. Foam tape works for smaller gaps and quick fixes. Compression strip nailed to the door stop is the most durable option.

Door Bottom

A door sweep screws to the door face and brushes the threshold. For the best seal, replace the threshold with a door shoe — it creates a positive compression seal and lasts much longer.

Window Channels

V-strip works well in double-hung window channels. For casements, use foam tape or compression strip on the window stop. Avoid foam tape on high-friction sliding surfaces.

Garage Door Perimeter

Magnetic weatherstripping is the top choice for steel garage doors. For wood doors, use compression strip with a kerf cut or a complete garage door bottom seal replacement.

Foam Tape Installation

1
Clean the surface: Remove old weatherstripping, dirt, and grease with rubbing alcohol. Adhesive won't stick to dusty or oily surfaces.
2
Measure and cut: Cut foam tape to length before removing the backing. Cut corners at 45° for a clean join.
3
Apply with door closed: Peel the backing and press the tape onto the door stop while the door is closed so the foam compresses correctly.
4
Test the seal: Close and latch the door. The tape should compress but still allow the door to close and latch without excessive force.

V-Strip Installation

1
Cut to length: Measure the door channel and cut V-strip with tin snips (metal) or scissors (plastic). Leave the strip slightly long and trim to fit.
2
Slide into channel: Open the door. Slide the V-strip into the groove between the door and the stop with the open side of the V facing the outside.
3
Nail or staple in place: Use a tack hammer to tap in the staples or small nails provided. Space 6–8 inches apart for metal; adhesive backing on plastic types.
4
Flare the V: Use a flat screwdriver to gently open the V flange so it presses firmly against the door edge when closed.

Door Sweep Installation

1
Measure door width: Cut the sweep to match door width exactly using a hacksaw or metal shears.
2
Position the sweep: Close the door. Hold the sweep against the bottom of the door so the brush or vinyl just touches the threshold. Mark the screw holes.
3
Pre-drill and fasten: Pre-drill pilot holes to avoid splitting the door. Drive screws snug but not over-tight.
4
Check clearance: Open and close the door several times to confirm the sweep does not drag or impede door movement.

Testing for Air Leaks

Candle Test

Hold a lit candle 1–2 inches from the door frame on a windy day. If the flame flickers or is drawn toward the gap, air is infiltrating. Move around the full perimeter.

Dollar Bill Test

Close the door on a dollar bill. If you can pull the bill out easily with no resistance, the seal is insufficient. You should feel significant drag when pulling the bill out.

Flashlight Test

On a dark night, have a helper shine a bright flashlight around the door perimeter from outside while you look for light leaking through from inside.

Common Mistakes

Over-compressing foam tape causes the door to stick. Placing sweep too low causes drag and premature wear. Using indoor foam tape outdoors — UV degrades it within months.

How to Use This Calculator

  1. 1
    Select the opening type — exterior door, sliding door, garage door, or window.
  2. 2
    Enter the dimensions in inches for width and height.
  3. 3
    Choose the weatherstripping type for material and cost per foot estimates.
  4. 4
    Select your gap size — how much space you can see or feel around the closed door.
  5. 5
    Enter your annual HVAC cost to see energy savings and payback period calculations.

Key Terms

CFM — Cubic Feet per Minute. Measures air infiltration rate through gaps. A 1/8" gap around a standard door can leak 2–5 CFM.
Door Stop — The molding strip on the door frame that the door closes against. Most weatherstripping mounts to or compresses against the door stop.
Kerf — A narrow groove cut into the door stop that accepts insert-style weatherstripping like bulb seals and compression strip inserts.
Compression Set — When foam weatherstripping permanently compresses over time and no longer springs back. The main reason foam tape needs replacement every 1–3 years.
Door Shoe — A metal threshold replacement that creates a positive seal between the door bottom and the floor; the most effective bottom-of-door solution.
Air Sealing — Sealing unintentional air leaks in the building envelope. Weatherstripping is one component; caulking around frames is another critical layer.

Frequently Asked Questions

How much weatherstripping do I need for a standard door?

A standard 36" x 80" exterior door has a perimeter of 232 inches (about 19.3 feet). With a 20% waste factor for cuts and overlap, plan for about 23–24 linear feet. Most hardware store weatherstripping kits come in 17 ft or 25 ft rolls — get the larger size for exterior doors.

How much energy can weatherstripping save?

A properly sealed home can reduce heating and cooling costs by 10–30%. Air leaks through doors and windows account for roughly 25–40% of residential heating and cooling energy. Sealing a single drafty door typically saves $30–$100 per year depending on your climate and energy costs.

How often should weatherstripping be replaced?

Foam tape typically lasts 1–3 years. V-strip and door sweeps last 5–10 years. Door shoes and compression strips can last 10–15 years. Check annually at the start of heating season — if you can see daylight or feel a draft with the door closed, it is time to replace.

What is the best weatherstripping for an exterior door?

For the top and sides, metal or high-quality EPDM compression strips are most durable. For the bottom, a door shoe is the most effective long-term solution. Avoid thin foam tape on high-traffic exterior doors — it compresses permanently within a year.

Can I weatherstrip a garage door myself?

Yes. For the bottom seal, most garage door hardware stores sell replacement bottom seal kits that slide into the existing retainer. For the perimeter, magnetic weatherstrip kits for steel doors are a simple DIY project. Replacing the complete bottom retainer and seal typically takes 1–2 hours.

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