Free Construction & Trades Calculators
These calculators are for builders, tradespeople and DIYers who need quantities and dimensions before they order or cut. Get bag counts, block counts, rafter lengths, joist spans and heating loads from your own measurements. Everything runs in your browser and nothing is uploaded.
Featured Construction & Trades tools
- Concrete & Mortar CalculatorAdds slabs, post holes and strip footings to one list and totals the bags and mix water.
- Stair Stringer CalculatorReturns riser height, tread depth and stringer length with an IRC and UK code check.
- Roof Shingle CalculatorTurns footprint and pitch into squares, bundles, underlayment and ridge cap.
- Room Heating & Cooling Load CalculatorGives the BTU per hour and kW a room needs from a heater or air conditioner.
Concrete, Masonry & Groundwork
6 toolsQuantities for pours, walls and hardcore, including the steel that goes in them.
- Construction / DIY
Concrete & Mortar Calculator
Add slabs, post holes, and strip footings to a project list and get total bags needed with mix water required.
- Concrete & Rebar
Rebar Weight Calculator
Get total weight and linear length by bar size, length and count, or estimate a slab grid mat. US #3-#18 and metric bar sizes, lap-splice allowance, cost per ton.
- Masonry / DIY / Landscapers
Concrete Block Wall Calculator
Enter wall dimensions and block size to get block count, mortar volume, and cement/sand bags. Wall elevation SVG and coursing layout.
- Bricklayers / DIY / Self-Builders
Brick Calculator
Enter wall area, brick format, and bond pattern to get brick count, mortar volume, and cement and sand bags. Deduct openings.
- DIY / Landscapers
Retaining Wall Block Calculator
Enter wall height, soil type, and block size to get minimum base width, footing depth, block count, and stability safety factor.
- Homeowners
Gravel Driveway Calculator
Add areas, stack base and top layers, pick a material, and get tons or tonnes, cubic yards, bag counts, and cost.
Framing, Roofs & Decks
7 toolsStairs, rafters, joists, beams, roofing, decking and fence posts.
- DIY / Builders
Stair Stringer Calculator
Enter total rise and run to get riser height, tread depth, stringer length, and IRC/UK building code compliance.
- DIY / Builders
Rafter Length Calculator
Enter building span, roof pitch, and overhang to get rafter length with birdsmouth notch dimensions. SVG cross-section diagram updates live.
- DIY / Builders
Floor Joist Span Calculator
Enter lumber species, joist size, spacing, and floor load to get maximum allowable span with L/360 deflection verdict.
- Structural DIY / Engineers
Beam Deflection Calculator
Enter beam span, load type, and cross-section to get midspan deflection, bending moment, and L/360 pass/fail verdict. SVG deflection diagram.
- Roofers
Roof Shingle Calculator
Enter footprint and pitch to get roof area, squares, bundles, underlayment, starter, ridge-cap linear feet, nails and cost.
- Deck Builders
Deck Board Calculator
Enter deck size, board width and gap to get board count, linear feet, boards by stock length with waste, joist count and fastener totals. Imperial or metric, live cost estimate.
- DIY / Contractors
Fence Post Spacing Calculator
Enter fence height, panel type, and wind zone to get maximum post spacing, footing depth, concrete volume, and post count.
Flooring & Tiling
3 toolsCoverage, grout and waste for tile and carpet.
- DIY / Tradespeople
Tile & Flooring Coverage Calculator
Enter room dimensions and tile size to get exact tile count, boxes needed, and cost estimate with a live cutting layout diagram.
- DIY / Tilers
Tile Grout Calculator
Enter tile dimensions, joint width, and area to get exact grout weight and bag count. Sanded vs unsanded recommendation, tile pattern SVG preview.
- Flooring / DIY / Homeowners
Carpet & Flooring Waste Calculator
Enter room dimensions, roll width, and pattern repeat to get total metres to order with correct waste factor. Roll count and offcut sizes.
Lumber & Joinery
2 toolsBoard footage for buying lumber and layout for dovetail joints.
- Woodworkers / Lumber Buyers
Board Feet Calculator
Enter lumber dimensions and quantity to get total board feet, cost, and a project materials list. Nominal vs. actual size guide, kerf waste toggle.
- Woodworkers / Furniture Makers
Dovetail Joint Spacing Calculator
Enter board width, tail count, and wood type to get tail spacing, pin width, angle in degrees, and a printable 1:1 SVG layout template.
Heating, Cooling & Moisture
4 toolsLoads, duct sizes, insulation values and condensation risk.
- HVAC / Homeowners
Room Heating & Cooling Load Calculator
Enter room dimensions, insulation quality, window area, and climate to get BTU/hr and kW needed for a heater or air conditioner.
- HVAC Technicians / Homeowners
HVAC Duct Size Calculator
Enter CFM and friction rate to get minimum round duct diameter, velocity, noise rating, and equivalent rectangular sizes.
- Builders / Architects / Homeowners
Wall U-Value & R-Value Builder
Add construction layers to get total R-value, U-value, and compliance check against UK Part L and Passivhaus targets.
- HVAC / Construction / Homeowners
Dew Point & Condensation Risk Calculator
Enter air temperature and relative humidity to get dew point and condensation risk on any surface. Mould risk indicator, dehumidifier sizing.
Pipes, Cables & Rigging
3 toolsPressure drop in pipe, working load on slings and sag in a cable.
- Plumbers / Engineers
Pipe Flow & Pressure Drop Calculator
Enter pipe diameter, flow rate, and length to get velocity, Reynolds number, flow regime, Darcy-Weisbach pressure drop, and head loss.
- Rigging / Construction / Lifting
Wire Rope & Rigging SWL Calculator
Enter sling configuration, rope rated load, and angle to get safe working load per leg with sling angle factor. ASME and EN safety notes.
- Engineers / Riggers / Sailors
Catenary Cable Sag Calculator
Enter span, cable weight, and tension or sag to get the other value plus cable length and an SVG catenary curve.
Which tool do I need?
- Order concrete for a slab or footingConcrete & Mortar Calculator
- Weigh rebar for a slabRebar Weight Calculator
- Count bricks or blocks for a wallBrick Calculator
- Work out stair rise and runStair Stringer Calculator
- Cut rafters for a given span and pitchRafter Length Calculator
- Check a floor joist spanFloor Joist Span Calculator
- Check beam deflectionBeam Deflection Calculator
- Estimate roof shingles and underlaymentRoof Shingle Calculator
- Count deck boards and joistsDeck Board Calculator
- Order tile and groutTile & Flooring Coverage Calculator
- Size a heater or air conditioner for a roomRoom Heating & Cooling Load Calculator
- Check the safe working load of a wire rope slingWire Rope & Rigging SWL Calculator
Construction & Trades FAQ
How many bags of concrete do I need?
Add each slab, post hole and strip footing to the concrete calculator. It totals the volume, converts it to bags and gives the mix water required.
How do I work out stair rise and run?
Enter the total rise and run into the stair stringer calculator. It returns the riser height, tread depth and stringer length, and checks the result against IRC and UK building code limits.
How many roof shingle bundles will I need?
Enter the roof footprint and pitch in the roof shingle calculator. It returns roof area, squares, bundles, underlayment, starter and ridge cap, nails and a cost estimate.
How much does rebar weigh?
The rebar weight calculator gives total weight and linear length by bar size, length and count. It covers US #3 to #18 and metric sizes, and includes a lap-splice allowance.
What does the joist span calculator check?
Enter the lumber species, joist size, spacing and floor load. It returns the maximum allowable span with an L/360 deflection verdict.
Do these calculators replace a building code check or an engineer?
No. They give estimates from the values you enter. Confirm structural and code questions with your local authority or a qualified professional before you build.
Related categories
Last updated: September 30, 2026