Siding Calculator
How much siding do I need? Calculate squares, panels, trim pieces, and costs for vinyl, fiber cement, wood, metal, and engineered wood siding. Accounts for doors, windows, and gable areas.
House Dimensions
House Perimeter (ft)
Wall Height (ft)
Siding Type
Ready to calculate
Enter your house dimensions
Last updated June 12, 2026 by our expert review team
Cost per Sq Ft by Siding Type
Material cost only. Installation adds $2-$6/sq ft depending on type and region.
Main walls
perimeter x height
Works for quick whole-house takeoffs.
Gables
triangle area
Often missed on ranches and garages.
Accessory trim
starter, J, corners
Order with the same color batch.
Expert Contributors
Hawkin
Certified Cost & Estimating Professional
AACE-certified estimator working with 20+ insulation companies including the two largest franchises in America.
See full profileEhsan Ghazanfari
Licensed Structural Engineer
FISE-certified structural engineer with 11+ years designing bridges, retaining walls, and foundations. MSc from Aalto University.
See full profileUpdated June 2026
How we verify our calculators
Pro Tips
For a modern farmhouse look, consider board and batten siding. It pairs well with horizontal lap siding as an accent on gable ends.
Always install house wrap (like Tyvek) before siding. It is your second line of defense against bulk water and prevents moisture from reaching the sheathing.
Leave a 1/4-inch gap at all butt joints for vinyl siding expansion. Vinyl expands and contracts significantly with temperature. Nailing too tight causes buckling.
Wood siding requires painting or staining every 5 to 7 years. Use our paint calculator to estimate how much exterior paint you need.
Fiber cement siding should be pre-primed and painted before installation. Factory-primed boards with a field-applied topcoat last 15+ years between repaints.
Overlap each course by at least 1.25 inches (vinyl) or per manufacturer specs. Insufficient overlap allows wind-driven rain behind the siding.
Start your first course perfectly level using a chalk line. Every subsequent course references the first, so errors compound quickly up the wall.
How the Calculator Works
This calculator is built for a fast siding takeoff, not a decorative wall-area guess. It starts with the body of the house: perimeter multiplied by wall height. Then it adds any gable area you enter separately, because gable triangles are where many siding orders come up short.
Door and window deductions are planning averages: 21 sq ft per door and 15 sq ft per window. That keeps the calculator quick for early ordering, but large patio doors, picture windows, garage doors, and window walls should be measured separately. Waste is applied after openings are deducted, then the answer is rounded up to full siding squares.
Trim is estimated from the same takeoff. J-channel surrounds openings, starter strip follows the bottom course, and corner posts follow the outside corners. The calculator does not size flashing, house wrap, fasteners, or specialty trim around meter boxes and hose bibs, so keep those on your supplier list.
Formula
Gross Area = Perimeter x Wall Height + Gable Area
Net Area = Gross Area - (Doors x 21) - (Windows x 15)
Order Area = Net Area x (1 + Waste%)
Squares = ceil(Order Area / 100)
Quick Reference
- 1 square
- 100 sq ft
- Avg door deduction
- 21 sq ft
- Avg window deduction
- 15 sq ft
- Standard waste
- 10%
- Vinyl expansion gap
- 1/4 inch
- Nail spacing (vinyl)
- 16 in. O.C.
Frequently Asked Questions About Siding
Should I subtract every window and door?
Subtract normal windows and doors for a cleaner material number. For a quick quote, average deductions are fine. For patio doors, garage doors, bay windows, or a sunroom wall, measure each opening because the averages will be too small.
How much waste should I use for siding?
Use 10% for a simple rectangle with lap siding. Use 15% for many corners, gables, dormers, or mixed materials. Use 20% when matching an older color or profile, because later batches may not match.
What does one square of siding mean?
One square is 100 sq ft of installed wall coverage. Suppliers often sell siding by the square or carton, so the calculator rounds order area up after waste instead of leaving a fractional square.
What trim should be ordered with siding?
Plan starter strip at the bottom course, J-channel around openings and roofline transitions, and corner posts at outside corners. Also ask your supplier about undersill trim, utility blocks, light blocks, and matching fasteners.
Can I install new siding over old siding?
Sometimes, but it hides sheathing problems and can trap moisture. A better takeoff assumes old siding comes off, damaged sheathing gets repaired, and new house wrap or WRB is installed before the finish siding.
Why does gable area matter so much?
A pair of gables can add several squares on a ranch, garage, or Cape Cod. Measure each triangle as base x height / 2, then add it to the wall area before waste.
Is vinyl, fiber cement, or engineered wood easiest to order?
Vinyl is usually easiest because accessories are standardized and color-matched. Fiber cement and engineered wood need closer attention to clearances, flashing, cut-end treatment, and board lengths.
What is not included in the siding estimate?
The calculator does not include house wrap, flashing tape, caulk, nails, starter clips, special mounting blocks, disposal, lift rental, or labor. Treat those as separate line items on the project quote.
Siding Estimates for Common Projects
One-Story Ranch Re-Side
120 ft perimeter, 9 ft walls, 60 sq ft gableThe risk is usually undercounting gables, not wall height. Walk the house and sketch each gable before ordering.
Two-Story Fiber Cement Body
160 ft perimeter, 18 ft walls, 200 sq ft gableFiber cement takeoffs should include cut-end treatment, flashing clearances, and extra pieces for high-wall breakage.
Mixed-Material Large Home
200 ft perimeter, 20 ft walls, 300 sq ft gableDo not blend lap siding, shake, and board-and-batten into one order. Measure each material zone and apply waste separately.
Detached Garage Match-In
96 ft perimeter, 10 ft walls, 48 sq ft gableGarage doors create big deductions, but they add trim complexity. Verify J-channel, utility trim, and color match before ordering.
Siding Mistakes That Cost You Money
Measuring only the first-floor walls
Siding takeoffs need all vertical wall areas, gables, dormers, garage returns, and bump-outs. Sketch each elevation so nothing disappears in a single perimeter number.
Using the same waste for every layout
A clean lap-siding rectangle may be fine at 10%. Stepped gables, many windows, and accent zones need more because short pieces and offcuts pile up fast.
Ordering siding without accessory trim
Starter strip, corners, J-channel, undersill trim, and mounting blocks should be ordered with the siding color. Missing trim can stop an install even when the wall panels are on site.
Ignoring water management
The finish siding is not the drainage plane. Plan house wrap, flashing tape, kickout flashing, and clearances before you focus on panel count.
Averaging unusual openings
Standard deductions are useful for a first pass. Measure garage doors, patio doors, large picture windows, and bay windows directly so the final order is not distorted.
Important Disclaimer
These estimates are for planning purposes only. Actual costs vary by location, material availability, and project complexity. Always get at least 3 local quotes. This calculator does not replace professional advice.