Tool Belt CalcFree trade calculators that show their working
Paint, concrete, framing, roofing, decking and more — worked out properly, with every assumption editable. No sign-up, and nothing you enter is ever sent to a server.
Work out how much paint, tile, concrete, mulch or board a project actually needs.
Paint Calculator
How many gallons a room needs, with doors and windows deducted.
Flooring Calculator
How many boxes of laminate, vinyl or hardwood a room needs.
Tile Calculator
How many tiles and boxes an area needs, at any tile size.
Concrete Calculator
Slab volume in cubic yards, and how many bags that works out to.
Mulch Calculator
How much mulch a bed needs, in cubic yards or bags.
Gravel Calculator
Gravel for a path or driveway, in tons and cubic yards.
Drywall Calculator
Sheets, screws, tape and compound for a room.
Roofing Calculator
Roof area, squares and shingle bundles from footprint and pitch.
Deck Board Calculator
Deck boards, joists and screws from your deck dimensions.
Fence Calculator
Posts, rails, pickets and post concrete for a fence run.
Sod Calculator
Rolls and pallets of sod for a lawn area.
Topsoil Calculator
Topsoil volume in cubic yards, tons or bags.
Paver Calculator
Pavers, base gravel and bedding sand for a patio or path.
Sand Calculator
Sand volume and weight for bedding, levelling or fill.
Asphalt Calculator
Tons of hot mix for a driveway or parking area.
Siding Calculator
Squares of siding for a house, with gables and openings.
Insulation Calculator
Bags or rolls of insulation for walls and attics.
Stair Calculator
Risers, treads, total run and stringer length from total rise.
Wallpaper Calculator
Rolls of wallpaper for a room, pattern repeat included.
Baseboard Calculator
Linear feet of baseboard, and how many lengths that is.
Rebar Calculator
Bar counts, linear feet and ties for a reinforced slab.
Brick Calculator
Bricks and mortar for a wall, at any common brick size.
Concrete Block Calculator
Blocks, courses and mortar for a block wall.
Stud Calculator
Studs and plate material for framing a wall.
Plywood Calculator
Sheets of plywood or OSB for a floor, wall or roof deck.
Plywood Cut List Optimizer
How many sheets, and exactly where to cut them.
Footing and Pier Calculator
Concrete for cylindrical footings, piers and post holes.
Ladder Angle Calculator
Ladder angle against the 4:1 rule, and the length you need.
Mixing Ratio Calculator
Split a total volume into two components at any ratio.
Dilution Ratio Calculator
Concentrate and water for any dilution ratio.
Sizing, airflow and performance calculations for heating and cooling.
BTU Calculator
Cooling BTU for a room, adjusted for height, sun and occupancy.
AC Size Calculator
Whole-house air conditioner tonnage from area, climate and insulation.
Furnace Size Calculator
Furnace BTU from heated area, climate and efficiency rating.
Mini Split Sizing Calculator
Mini split head size for a room, matched to real unit sizes.
Duct Size Calculator
Round and rectangular duct size from CFM and target velocity.
CFM Calculator
Airflow in CFM from room volume and target air changes.
Static Pressure Calculator
Total external static pressure against the air handler's rating.
SEER Savings Calculator
Annual running cost difference between two SEER ratings.
Delta T Calculator
Temperature split between return and supply air, assessed.
Bathroom Fan CFM Calculator
Extractor fan size for a bathroom, by both common rules.
Tons to BTU Calculator
Convert cooling tons to BTU per hour and kilowatts.
Tyres, gearing, engine geometry, economy and towing, worked properly.
Tire Size Calculator
Compare two tire sizes by overall diameter and percentage difference.
Speedometer Error Calculator
True speed and error after fitting a different tire size.
Gear Ratio Calculator
Axle ratio from tooth counts, and overall drive ratio.
RPM at Speed Calculator
Engine rpm at any road speed from tires and gearing.
Engine Displacement Calculator
Displacement from bore, stroke and cylinder count.
Compression Ratio Calculator
Static compression ratio from chamber, gasket, deck and piston volumes.
Horsepower Calculator
Horsepower from torque and engine speed, plus kilowatts.
Quarter Mile Calculator
Quarter mile ET and trap speed from weight and power.
MPG Calculator
Fuel economy in mpg, L/100 km and km per litre.
Fuel Cost Calculator
Fuel cost for a trip, and cost per mile.
Wheel Offset Calculator
Convert between wheel offset and backspacing.
Towing Capacity Calculator
Maximum trailer weight from GCWR and what you are carrying.
Ohm's law, voltage drop, power conversions, kVA and generator sizing.
Ohm's Law Calculator
Resistance and power from voltage and current.
Voltage Drop Calculator
Voltage drop over a run, checked against the 3% target.
Watts to Amps Calculator
Convert watts to amps at any voltage, with power factor.
kVA to Amps Calculator
Transformer kVA to full load amps, single or three phase.
Generator Sizing Calculator
Generator size from running load and motor starting surge.
Electricity Cost Calculator
Daily, monthly and annual running cost of an appliance.
Fractions, areas, volumes, angles, scale and machining speeds.
Fraction to Decimal Calculator
Decimal inches to the nearest tape measure fraction.
Board Foot Calculator
Board feet and cost from lumber dimensions.
Roof Pitch Calculator
Roof pitch to degrees, grade and slope factor.
Slope and Grade Calculator
Slope as percentage, degrees, ratio and fall per foot.
Drawing Scale Converter
Convert a measurement off a drawing into the real dimension.
Torque Conversion Calculator
Convert torque between lb-ft, Nm, lb-in and kgf-m.
Square Footage Calculator
Square footage for rectangles, circles and triangles.
Cubic Yards Calculator
Volume in cubic yards from area and depth.
Pipe Volume Calculator
How much a length of pipe holds, in gallons and litres.
Linear Feet Calculator
Linear feet from room size, and how many lengths that is.
SFM to RPM Calculator
Spindle rpm from cutting speed and diameter.
Feeds and Speeds Calculator
Feed rate from spindle speed, flutes and chip load.
Tap Drill Size Calculator
Tap drill size from thread size and target engagement.
Material Weight Calculator
Weight of bar, plate and tube in common metals.
Lumber Size Chart
What nominal lumber sizes actually measure.
Wire Gauge Chart
AWG sizes with diameter, circular mils and mm².
Drill Size Chart
Fractional drill sizes in decimal and millimetres.
Screw Size Chart
Screw gauges with diameters and pilot hole sizes.
Sheet Metal Gauge Chart
Sheet steel gauge thicknesses and weights.
Sandpaper Grit Chart
Which grit for which job, and the sequence.
Miter and bevel angles, rafters, tapers, arcs and flat patterns.
Trapezoid Calculator
Taper angle, cut length and area for a tapered piece.
Compound Miter Calculator
Miter and bevel settings for crown moulding and sloped corners.
Miter Angle Calculator
The miter cut for any corner, square or not.
Polygon and Segment Calculator
Miter angle and segment length for any regular polygon.
Rafter Calculator
Common rafter length and cut angles from span and pitch.
Squaring and Diagonal Calculator
The diagonal that proves a corner is square.
Arc and Chord Calculator
Radius and arc length for an arched opening.
Kerf and Yield Calculator
Real yield per stick once blade kerf is counted.
Sheet Metal Bend Allowance Calculator
Flat pattern length and bend deduction for sheet metal.
Budget a project — decks, roofs, concrete, fencing, flooring and more.
Deck Cost Calculator
What a new deck costs, by size, material and railing.
Roof Replacement Cost Calculator
What a roof replacement costs, including tear-off.
Concrete Slab Cost Calculator
What a concrete slab costs, materials and placing.
Fence Cost Calculator
What a fence costs per foot, installed, with gates.
Flooring Cost Calculator
What a new floor costs, fitted, including removal.
Interior Painting Cost Calculator
What it costs to have a room painted.
Drywall Cost Calculator
What drywall costs hung, taped and finished.
Driveway Cost Calculator
What a driveway costs, by size and surface type.
Recently added
BTU Calculator
Cooling BTU for a room, adjusted for height, sun and occupancy.
AC Size Calculator
Whole-house air conditioner tonnage from area, climate and insulation.
Furnace Size Calculator
Furnace BTU from heated area, climate and efficiency rating.
Mini Split Sizing Calculator
Mini split head size for a room, matched to real unit sizes.
Duct Size Calculator
Round and rectangular duct size from CFM and target velocity.
CFM Calculator
Airflow in CFM from room volume and target air changes.
Static Pressure Calculator
Total external static pressure against the air handler's rating.
SEER Savings Calculator
Annual running cost difference between two SEER ratings.
Why use these instead of the first result you find
Everything runs locally
There is no server to send anything to. No account, no analytics script, no cookies, no logs. What you generate exists in your browser tab and nowhere else — which is the only guarantee that actually means anything.
Built properly, not mass-produced
Every calculator exposes its assumptions as editable fields rather than hiding a coverage rate behind a constant, itemises every step of the working, and says plainly where arithmetic stops and engineering begins.
Fast and accessible
Pages are prerendered static HTML with a small amount of JavaScript for the tool itself. Everything is keyboard operable, screen-reader labelled, and works from a phone to a desktop.