Square Footage Calculator for Contractors

Miscalculating square footage is expensive. Under-order and you're scrambling for more material mid-job. Over-order and you're eating the cost. This calculator handles the four most common shapes contractors encounter, plus lets you dial in the right waste factor so you order exactly what you need.

square_foot Select Shape

📐 Length × Width = Area

Length in feet

Width in feet

📐 Rectangle A + Rectangle B = Total Area

Split the L into two rectangles. Measure each section separately.

Section A — Length in feet

Section A — Width in feet

Section B — Length in feet

Section B — Width in feet

📐 (Base × Height) ÷ 2 = Area

Base in feet

Height perpendicular height, in feet

📐 π × Radius² = Area

Diameter OR Radius enter one

Diameter in feet

Radius in feet

recycling Waste Factor

10%

Straight lay: 5–10% | Diagonal/complex: 10–15% | High-end materials: 15–20%

calculate Results

Total Sq Ft to Order (with waste)

169 sq ft

300

Net Sq Ft

Waste Buffer

Waste Factor Guide by Trade

Flooring

Hardwood, LVP, laminate: 5–10% for straight lay. Add 10–15% for diagonal or herringbone patterns. Tile: 10% minimum, 15% for diagonal or natural stone.

Roofing

Standard roofs: 10–15% waste. Complex roofs with multiple valleys, hips, and dormers: 15–20%. Add extra for starter strips and ridge cap.

Drywall

5–10% for most rooms. Add more for rooms with lots of windows, doors, or angles that create small cut pieces.

Paint

Paint coverage is typically 350–400 sq ft per gallon on smooth surfaces. Add 10–20% for textured surfaces or porous materials needing two coats.

Frequently Asked Questions

What waste factor should I use for flooring?

For simple rectangular rooms with straight-lay flooring, use 5–10%. For diagonal patterns, complex shapes, or tile work, use 10–15%. For high-end materials or intricate patterns, use 15–20% to be safe.

How do I calculate square footage for an L-shaped room?

Split the L-shape into two rectangles. Measure each rectangle's width and length, calculate their areas separately, then add them together. Our L-shape calculator does this automatically — just enter each section's dimensions.

Why do I need to add waste to square footage?

Waste accounts for cuts, breakage, pattern matching, and unusable pieces from cuts. Ordering without waste means you'll almost always run short and have to reorder — often at a higher price or from a different dye lot, which can cause visible color differences.