Siding Calculator
Estimate siding area, squares and material cost.
Project details
Enter your measurements below.
Exterior siding starts with wall geometry, then product coverage takes over
Siding quantity is based on the exterior surfaces that will actually be clad. Rectangular walls are straightforward, but gables, garage doors, large windows and multiple elevations make one overall length × height calculation too rough. Measure each elevation, add triangular or other shapes separately and deduct major openings when appropriate. Then use the coverage per carton, panel or square for the exact siding product. Corners, starter pieces, J-channel, trim and flashing are accessory quantities rather than invisible additions to the field-siding area.
Separate wall faces and gables so unusual shapes are visible.
Use the installed coverage stated for the selected siding carton/panel.
Corners, trim, starter, channels and flashing need their own takeoff.
How to use the Siding Calculator
- Measure each exterior wall surface receiving siding and calculate its area.
- Add gables or triangular wall sections using their actual shape rather than treating them as full rectangles.
- Deduct significant openings if that is appropriate for the product and takeoff method.
- Apply a layout/cut allowance, then convert adjusted area to the selected siding's whole cartons, panels or squares.
Why elevations are worth measuring separately
A house can have the same perimeter but very different siding area depending on story heights, gables and openings. Elevation-by-elevation measurement keeps those differences visible.
Use field coverage as one part of the order
Carry the calculated siding quantity into a separate accessory takeoff for corners, starter strips, trim, channels and flashing required by the selected system.
Worked example: wall plus gable
- Rectangular wall
- 30 ft × 9 ft = 270 sq ft
- Gable
- ½ × 30 ft × 6 ft = 90 sq ft
- Large openings
- 60 sq ft
- Net area
- 300 sq ft
The field area is about 300 sq ft before any cut allowance. That area can then be divided by the selected product's installed package coverage.
Practical planning tips
Measure gable height from the top of the rectangular wall to the peak; do not use the full wall height twice.
Use installed coverage for lap siding because physical piece dimensions may include overlap that does not cover new wall area.
Treat different materials—such as stone veneer below and siding above—as separate wall bands.
Keep a sketch of each elevation so deductions and triangular additions can be checked before ordering.
Common mistakes to avoid
Using house floor area or perimeter alone as siding area.
Counting a gable as a full rectangle and doubling the triangular portion.
Deducting every small opening even when surrounding cuts mean the siding saving is negligible.
Assuming field siding coverage also includes corner posts, starter or trim.
Siding Calculator FAQs
How do I calculate siding on a gable?+
Treat the gable as a triangle: one-half × base width × vertical gable height, then add it to the rectangular wall below.
Should windows and doors be deducted?+
Large openings can be deducted for a closer field-area estimate. Small openings may not save much material after surrounding cuts, so use judgment and the product takeoff method.
What coverage should I use?+
Use the installed coverage per carton, panel or square supplied for the exact siding product.
Does this calculator include trim?+
No. Corners, starter, channels, soffit/fascia and flashing should be measured separately.