From flooring and paint to grading a driveway, most construction estimates come down to a few pieces of geometry done carefully. These calculators handle the area and slope maths so you can price materials, order the right quantity, and plan site work with confidence, and each one shows the formula and the working.

Seven Construction Calculators

Square Footage Calculator - Finds the area of a rectangular, circular, or triangular space in square feet, square metres, and square yards. Enter dimensions in feet, inches, yards, or metres, and add a price per square foot to get the total material cost for flooring, tiling, turf, or decking.

Wall Square Footage Calculator - Calculates the paintable or coverable wall area of a room from its length, width, and ceiling height, then subtracts doors and windows. Returns gross area, opening area, net area, and an estimate of the paint needed based on typical coverage.

Elevation Grade Calculator - Works out the slope of a ramp, driveway, roof, or piece of land from the rise and the run. Returns the grade as a percentage, the angle in degrees, the slope length, and the rise-to-run ratio.

Gravel Calculator - Estimates how much gravel a driveway, path, or bed needs, in both volume and weight. Enter the length, width, and depth of the area and pick a material, and it returns the volume in cubic metres and the weight in tonnes and kilograms, using bulk density presets for gravel, sand, crushed stone, and topsoil.

Rebar Calculator - Estimates the total rebar length and weight needed for a rectangular slab’s two-way reinforcement grid. Enter the slab dimensions, bar spacing, and US rebar size, and it returns the total length, weight, and bar count.

Roofing Calculator - Converts a building footprint and roof pitch into true sloped roof area, roofing squares, and shingle bundles needed. Enter length, width, and pitch (rise per 12 inches of run), and add a price per square for an estimated material cost.

Drywall Calculator - Calculates how many sheets of drywall a room needs from its dimensions, an optional ceiling area, and a choice of 4x8, 4x10, or 4x12 sheet sizes. Returns the total area and the sheet count needed after a waste allowance, rounded up.

Why Area and Slope Estimates Matter

Ordering materials by area is where budgets are won or lost. Underestimate the square footage and you make a second trip and pay premium prices; overestimate and you pay for waste. The Square Footage Calculator and Wall Square Footage Calculator give you defensible quantities for flooring, paint, and drywall. Slope matters for drainage, accessibility, and safety: a ramp that is too steep fails code, and land that is too flat does not drain. The Elevation Grade Calculator turns a rise and run into the grade and angle you need.

Frequently Asked Questions

How do I calculate square footage?

For a rectangular area, multiply length by width in feet. A room 12 feet by 10 feet is 120 square feet. The Square Footage Calculator also handles circles and triangles and converts to square metres and square yards.

How much wall area do I need to paint?

Multiply the room perimeter by the ceiling height, then subtract the doors and windows. For a 12 by 10 foot room with 8 foot ceilings, one door and two windows, that is about 301 square feet. The Wall Square Footage Calculator does this and estimates the paint needed.

How do I calculate the grade of a slope?

Divide the rise by the run and multiply by 100 for the percentage grade. A 3 foot rise over 100 feet of run is a 3 percent grade. The Elevation Grade Calculator also gives the angle in degrees and the slope length.

How much extra material should I order?

Add roughly 5 to 10 percent to the calculated area for waste from cuts and breakage, and more for patterned tiles or diagonal layouts. Always round up to whole boxes or tins when ordering.

How do I calculate how many shingles a roof needs?

Divide the building footprint by the cosine of the pitch angle to get true roof area, convert to roofing squares (100 square feet each), add a waste allowance, and multiply by 3 bundles per square. The Roofing Calculator does this from the footprint and pitch.

How many sheets of drywall does a room need?

Multiply the room perimeter by the ceiling height for wall area, add the ceiling area if you are drywalling it, divide by the sheet size, add a waste allowance, and round up. The Drywall Calculator handles this for 4x8, 4x10, and 4x12 sheets.

Construction Calculators