BuildNumerics Guides
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Practical guides for construction calculations, material estimating and field measurements — each one links to the BuildNumerics calculator that does the math.
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How to Calculate Concrete Volume for a Slab
Concrete volume for a slab is length × width × depth, converted to a single unit. Here's the formula, the unit traps, and a worked example.
How Much Concrete Do I Need?
A walkthrough for sizing a concrete order — the formula for your shape, a waste allowance, ready-mix or bags, and the difference between the exact figure and what you actually order.
How to Calculate Roof Area From Roof Dimensions
Roof area isn't the same as the building's footprint — the slope factor from the pitch stretches a flat area into the real sloped surface.
How to Calculate Tile and Flooring Quantity
Tile and flooring quantity starts with room area, then adds a cut-waste allowance that depends heavily on the layout pattern you choose.
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How to Calculate Concrete Volume for a Slab
Concrete volume for a slab is length × width × depth, converted to a single unit. Here's the formula, the unit traps, and a worked example.
How Much Concrete Do I Need?
A walkthrough for sizing a concrete order — the formula for your shape, a waste allowance, ready-mix or bags, and the difference between the exact figure and what you actually order.
How to Calculate Concrete With Waste
Waste allowance turns a mathematical volume into a realistic order quantity. Here's how much to add and why it's never applied silently.
How to Calculate Concrete for Fence Posts
Fence-post concrete isn't the hole volume alone — it's the hole minus the post that sits inside it, repeated per post.
How to Calculate Concrete for Footings
A footing is calculated the same way as a slab — length × width × depth — but often needs to be split into multiple sections for a stepped or T-shaped profile.
How to Calculate Roof Area From Roof Dimensions
Roof area isn't the same as the building's footprint — the slope factor from the pitch stretches a flat area into the real sloped surface.
How to Calculate Roof Pitch
Roof pitch is rise over run, written as X-in-12. Here's how to measure it three ways and convert it to degrees, percent slope and a slope factor.
How Many Shingles Do I Need?
Shingles are bought by the bundle: roof area ÷ 100 gives squares, squares × bundles per square gives bundles, and waste plus any starter and ridge caps go on top.
How to Calculate Tile and Flooring Quantity
Tile and flooring quantity starts with room area, then adds a cut-waste allowance that depends heavily on the layout pattern you choose.
How to Calculate Paint Needed for a Room
Paint quantity is wall area (with doors and windows subtracted) divided by the paint's actual coverage rate, times the number of coats.
How to Calculate Brick and Mortar Quantity
Brick count comes from wall area and the brick's exposed face size, including the mortar joint. Mortar is a separate estimate, based on the units laid, the joint size and the mortar product.
How to Calculate Rebar Quantity for Concrete
Rebar quantity comes from the reinforcement design — bar spacing and grid size — not from the concrete volume it reinforces.
How to Calculate Board Feet of Lumber
A board foot is a unit of lumber volume — 144 cubic inches — used for pricing and ordering, distinct from a linear foot of a specific board.
How to Calculate Plywood Requirements
Plywood is ordered by the sheet — divide the area to cover by the sheet's coverage, then add waste for cuts and layout inefficiency.
How to Calculate Drywall Sheets Needed
Drywall sheet count comes from total wall and ceiling area divided by sheet coverage, with a modest waste allowance for cuts.
How to Calculate Insulation Requirements
Insulation quantity depends on the area to cover and the specific product's coverage per package at your target R-value.
How to Calculate Mulch Quantity
Mulch quantity is bed area times the desired depth, converted to cubic yards for bulk orders or bags for smaller beds.
How to Calculate Paver Sand and Base Material
A paver installation needs a compacted base layer and a bedding sand layer — two separate volume calculations, not one combined figure.
How to Calculate Gravel Needed for a Project
Gravel is calculated by volume like concrete, but ordering by weight (tons) means factoring in the specific material's density.
How to Calculate Gravel for a Driveway
A gravel driveway is usually built in layers with a greater total depth than a path, to support vehicle loads over time.
How to Calculate Excavation Volume
Excavation volume follows the same length × width × depth logic as a concrete slab, but real sites often need sectioning for varying depth.
How to Calculate Topsoil Quantity
Topsoil quantity follows the familiar area × depth formula, with typical depths depending on whether you're leveling, filling, or starting a lawn.
Prime Coat vs Tack Coat: What's the Difference?
A prime coat bonds a granular base to the first asphalt layer; a tack coat bonds one asphalt layer to another. They're not interchangeable.
How to Calculate Plastering Material Requirements
Plastering quantity comes from wall/ceiling area times the plaster coat's thickness, similar to a very thin concrete or mortar volume.
How to Read a Sieve Analysis
A sieve analysis reports how much material is retained on each sieve size — here's how to turn that into percent passing and a gradation curve.
Los Angeles Abrasion Test: What the Result Means
The LA abrasion test tumbles aggregate with steel balls and measures how much breaks down — the result is a percent loss, lower generally being tougher.
How to Calculate Aggregate Specific Gravity
Specific gravity compares an aggregate's mass to an equal volume of water — a key input for concrete and asphalt mix design calculations.
How to Calculate Soil Moisture Content
Moisture content is the water lost when a soil sample is oven-dried, expressed as a percentage of the sample's dry weight — not its total weight.
Atterberg Limits Explained: Liquid, Plastic and Shrinkage Limits
Atterberg limits mark the moisture contents where fine-grained soil shifts between solid, plastic and liquid behavior — key inputs for soil classification.
How to Calculate CBR (California Bearing Ratio)
CBR is the corrected test load at 2.5 mm or 5.0 mm penetration divided by a standard load, times 100. Here's how to get the loads, correct the curve and report the result.