Siding calculator
Walls and gables minus openings, siding by the box or piece, corners, J-channel, starter, house wrap, tape and nails.
Job
Siding
Calculated — type to override
Walls & gables
Walls
Measure each wall from corner to corner, bottom of siding to soffit.
Gables (triangles)
Openings (deducted)
Windows & doors
Rough size of the trim or frame, in inches.
Corners & trim
Calculated — type to override
Top of walls (vinyl)
Weather barrier
Materials list
| Item | Qty | Unit price | Cost |
|---|---|---|---|
| Siding | |||
| Vinyl (double 4 in.)1,295 sq ft net at 200 sq ft/box | 8 boxes | $ | — |
| Trim & accessories | |||
| Starter strip134 LF | 12 pcs (12 ft) | $ | — |
| Outside corner posts4 corners × 9 ft | 4 pcs (10 ft) | $ | — |
| J-channel230 LF: openings, rakes | 21 pcs (12 ft 6 in.) | $ | — |
| Undersill (utility) trim170 LF: under windows, tops of walls | 16 pcs (12 ft) | $ | — |
| Weather barrier | |||
| House wrap1,485 sq ft + 10% laps | 2 rolls | $ | — |
| Seam tape | 3 rolls (165 ft) | $ | — |
| Window & door flashing tape (4 in.)199 LF of opening perimeter | 3 rolls (75 ft) | $ | — |
| Cap nails / cap staples | 1 boxes (1,000) | $ | — |
| Fasteners & sealant | |||
| Roofing nails, 1-1/2 in. (galvanized)≈ 1,911 nails | 11 lb | $ | — |
| Sealant (openings, penetrations) | 2 tubes | $ | — |
| Mounting / split blocks (lights, outlets, faucets, vents) | 4 ea | $ | — |
How it works
- Net area = walls + gable triangles − windows and doors. One square is 100 sq ft.
- Lap siding coverage per piece = exposure × length (8-1/4 in. fiber cement at 7 in. × 12 ft = 7 sq ft).
- Vinyl J-channel runs up both sides and across the top of every opening and along the rakes; windows get undersill trim below.
- Add your supplier's unit prices to any line for a cost estimate; tax and markup are optional.
How to measure
- Measure each wall corner to corner and from the bottom of the siding to the soffit.
- Gables: base width and height from the top of the wall to the peak.
- Openings: measure the outside of the window or door frame in inches.
Estimates only. Coverage, sizes and waste vary by product and job — verify with the manufacturer's specs and your local building code before ordering.
Doing soffit and fascia too? Soffit, fascia & trim calculator →