How-to building calculators
25 specific building math questions, each answered with a live calculator, the manual formula worked out step by step, a quick-reference table and FAQs.
Concrete & Masonry
How to Calculate Concrete for a 20x20 Patio (Free AI Tool)
Work out exactly how many cubic yards of concrete a 20x20 patio needs at 4 in or 6 in thick, with bag counts, waste allowance and the manual formula.
Open calculatorHow Much Rebar Do I Need for a Concrete Slab?
Calculate rebar for any concrete slab: bars per direction, total linear feet, lap allowance and bar size guidance for 4 in and 6 in residential slabs.
Open calculatorConcrete Block Calculator With Aggregate Breakdown
Count CMU blocks per wall and break the job down into mortar bags, sand and core-fill aggregate, with the manual math for every step.
Open calculatorHow Many Bags of Concrete Mix for Fence Posts?
Find the number of 50 lb or 80 lb fast-setting bags per fence post hole, with hole depth and diameter rules and the manual volume math.
Open calculatorEstimate Gravel and Sand Ratio for Cement Mixing
Get cement, sand and gravel quantities for any mix ratio and volume, including the 1:2:3 rule, bulking factor and bags of portland per cubic yard.
Open calculatorFraming & Carpentry
How Many Studs Do I Need for a 10 Foot Wall?
Count studs, plates and corner framing for a 10 ft wall at 16 or 24 in on centre, with the manual formula and openings allowance.
Open calculatorRafter Length Calculator for a Gable Roof
Calculate common rafter length from span, pitch and overhang using the rise-over-run method, with pitch multipliers and rafter counts.
Open calculatorHow Much Lumber to Build a Backyard Deck
Estimate decking boards, joists, beams, posts and fasteners for any backyard deck size, with joist spacing rules and a 10% cut-waste allowance.
Open calculatorDrywall Sheet Calculator With Wastage Percentage
Count drywall sheets for walls and ceilings with an adjustable waste percentage, plus joint compound, tape and screw quantities.
Open calculatorCalculate Distance Between Floor Joists for Subfloor
Work out joist spacing and count for a subfloor, with 16 vs 19.2 vs 24 in on centre guidance and the sheathing thickness each spacing requires.
Open calculatorFlooring & Tiling
Square Footage Calculator for Irregular Shaped Rooms
Measure L-shaped, angled and curved rooms by breaking them into rectangles and triangles, then total the square footage for flooring or paint.
Open calculatorHow Many Tiles Do I Need for a 5x8 Bathroom?
Find the tile count for a 5x8 bathroom floor in every common tile size, with waste percentages for straight and diagonal layouts.
Open calculatorCalculate Flooring Square Footage With 10 Percent Waste
Add the right waste percentage to your flooring order — 10% straight lay, 15% diagonal — and convert square feet into boxes you can actually buy.
Open calculatorLaminate Flooring Box Calculator for Home DIY
Turn room square footage into boxes of laminate, plus underlayment, transitions and trim — with the waste factor built into the math.
Open calculatorHow Much Grout and Mortar Do I Need for Tiling?
Estimate thin-set mortar and grout by tile size, joint width and trowel notch, with coverage figures per bag for floors and walls.
Open calculatorEarthwork & Roofing
How Many Cubic Yards of Soil Do I Need for Raised Beds?
Calculate cubic yards and bags of soil for raised garden beds of any size, plus the recommended soil, compost and aeration blend.
Open calculatorCalculate Roof Shingles Bundle Count From Square Footage
Convert roof square footage into squares and bundles of shingles, including pitch multipliers, starter, ridge cap and a 10% waste allowance.
Open calculatorHow Much Mulch Do I Need for a Large Garden Bed?
Work out cubic yards and bags of mulch for large beds at 2, 3 or 4 inch depth, with the bulk vs bagged break-even point.
Open calculatorRetaining Wall Block Calculator With Stepped Base
Count retaining wall blocks, caps, base gravel and drainage stone, including how to step the base course on sloping ground.
Open calculatorCalculate Dirt Removal Volume for Foundation Digging
Calculate excavation volume in cubic yards, apply the soil swell factor, and convert to truck loads for foundation and footing digs.
Open calculatorAI & Smart Estimation
Free AI Construction Material Estimator Online
Describe your project in plain English and get a materials list, quantities, waste allowance and a planning cost range — free, no signup required.
Open calculatorInstant Building Material Calculator for DIY Projects
Instant material quantities for DIY projects — concrete, lumber, drywall, tile, mulch and more — with formulas, waste and shopping lists.
Open calculatorVoice Activated Construction Math Calculator
Do construction math hands-free on site: dictate the project into the AI planner and get volumes, counts and conversions without typing.
Open calculatorSmart App to Estimate Home Renovation Materials
Plan a whole renovation, not one material: combined material lists, cost ranges, tool lists and shopping lists for kitchens, baths and additions.
Open calculatorAutomated Material Takeoff Tool for Small Contractors
Produce a fast material takeoff for small residential jobs — quantities, waste, assumptions and a printable shopping list you can quote from.
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