Question 1

How do I calculate concrete for a slab?

Accepted Answer

Multiply the length × width × depth of your slab in feet. Divide by 27 to convert cubic feet to cubic yards. Add 10% for waste. For example, a 20×20 ft slab that is 4 inches thick needs (20 × 20 × 0.33) / 27 ≈ 4.9 cubic yards. Our concrete calculator does this math instantly.

Question 2

How many shingles do I need for my roof?

Accepted Answer

Measure your roof area in square feet, then divide by 100 to get the number of "squares." Each square requires 3 bundles of standard three-tab shingles. Add 10–15% for waste, ridges, and hips. A 2,000 sq ft roof needs roughly 60–69 bundles.

Question 3

How do I estimate gravel for a driveway?

Accepted Answer

Multiply length × width × depth (in feet). Divide by 27 for cubic yards. Gravel weighs about 2,800 lbs per cubic yard. A typical 12 ft × 50 ft driveway with 4 inches of gravel needs roughly 7.4 cubic yards or about 10 tons.

Question 4

What is a board foot and how do I calculate it?

Accepted Answer

A board foot is a unit of lumber volume equal to 144 cubic inches — equivalent to a 1 ft × 1 ft × 1 inch board. Calculate it as: (thickness in inches × width in inches × length in feet) / 12. For example, a 2×6×8 ft board is (2 × 6 × 8) / 12 = 8 board feet.

Question 5

How much paint do I need for a room?

Accepted Answer

One gallon of paint covers approximately 350–400 square feet. Measure the total wall area (perimeter × height), subtract windows and doors, then divide by 350. Most rooms need 2 coats, so double the amount. A 12×12 ft room with 8 ft ceilings typically needs about 2 gallons for 2 coats.

Question 6

How do I calculate roof pitch?

Accepted Answer

Roof pitch is expressed as rise over run — for example, a 6/12 pitch rises 6 inches for every 12 inches of horizontal distance. Measure the vertical rise from the top of a level to the roof surface over a 12-inch horizontal span. You can also convert to degrees: a 6/12 pitch equals about 26.6°.

Question 7

How many bricks do I need for a wall?

Accepted Answer

For standard US bricks (3⅝ × 2¼ × 8 inches) with ⅜-inch mortar joints, you need approximately 7 bricks per square foot of wall. Multiply the wall area by 7, then add 5–10% for waste and cuts. A 100 sq ft wall requires roughly 735–770 bricks.

Question 8

Are these construction calculators free to use?

Accepted Answer

Yes. Every calculator listed on this page is completely free to use. Trade Website Professionals provides these tools as a resource for contractors, builders, and DIYers to save time on material estimates. No account or signup required.

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