ProReckoner's tradie calculators are built for on-site use — fast on mobile, accurate in the field. Tools cover concrete estimating, carpentry (timber, decking, stud framing, rafters), electrical (Ohm's Law, airflow), tiling (grout, adhesive, tile count), plumbing (pipe fall, water pressure), solar (system sizing, panels, savings, inverter), plus general builders tools (roof pitch, stairs, area, weight) and quoting. All tools support metric and imperial units.
General & Building
6 toolsConcrete Calculator
Bags or m³ for slabs, footings and post holes. Supports 20kg, 25kg and 40kg bags. Includes 10% waste.
Volume = L × W × D (+ 10% waste)
Standard slab: 100mm deep. Footings typically 300mm+ deep. Always add 10% for spillage and uneven ground.
Paint Coverage Calculator
Litres of paint needed for any surface area. Enter coats, coverage rate and waste factor.
Litres = (Area × Coats × Waste) ÷ Coverage
Always check the coverage rate on the actual tin — it varies by product and surface porosity.
Area & Volume Calculator
Rectangle, triangle, circle area or room volume. Useful for estimating materials across any trade.
Rectangle: L × W · Triangle: ½ × B × H · Circle: π × r²
Roof Pitch Calculator
Roof pitch angle from span and rise, or from a rise:run ratio. Calculates rise and rafter length.
Rise = Run × tan(pitch) · Rafter = Run ÷ cos(pitch)
Common pitches: 15° (low), 22.5° (standard), 30° (steep), 45° (Dutch gable).
Stair Calculator
Number of risers, riser height, going and total run from floor-to-floor height. Checks AS 1657 compliance.
Material Weight Calculator
Weight of steel plate, concrete slabs, aluminium sheet and structural timber from dimensions.
Carpentry
4 toolsTimber / Lineal Metres Calculator
How many lengths of timber to order for any area or run. Covers decking, cladding, flooring and framing. Includes gap spacing and waste allowance.
Rows = Area ÷ (Board width + Gap in m)
Lineal metres = Rows × Run length × (1 + waste%)
Waste guide: Straight run: 10% · 45° diagonal: 15–20% · Complex pattern: 20–25%Always round up to full lengths — short offcuts have limited reuse value.
Decking Calculator
Boards, lineal metres, fixings and waste for a deck area. Supports screw and hidden clip fixing systems.
Boards across = Deck width ÷ (Board width + Gap)
Lineal metres = Boards across × Deck length × (1 + waste%)
Gap tips: Hardwood 5–6mm (expands in wet) · Treated pine 6–8mm · Allow for movement with seasoned timber.
Joist spacing: 450mm max for 90mm boards · 600mm for 140mm+.
Stud Spacing Calculator
Number of studs, noggins and plate timber for a wall frame. Supports 450mm and 600mm stud centres. Accounts for corner framing.
Studs = floor(Wall length ÷ Spacing) + 1
Standard stud spacing: 450mm (standard sheets 1350mm wide) or 600mm (1200mm sheet module)Add king studs + jack studs for each door/window opening — not included in this calculation.
Corner framing typically requires 3 studs per internal or external corner.
Rafter Length Calculator
True rafter length, rise, ridge height and overhang from roof span and pitch angle. Works alongside the Roof Pitch calculator above.
Run = Span ÷ 2 (half span)
Rise = Run × tan(pitch)
Rafter = Run ÷ cos(pitch)
With overhang = Rafter + (overhang ÷ cos(pitch))
Add 100mm minimum at ridge for plumb cut · Add 50mm at seat cut for tolerance.Always verify rafter sizing with a structural engineer for spans over 4m.
Electrical
3 toolsOhm's Law Calculator
Find voltage, current, resistance or power from any two known values. V = IR · P = VI.
V = I × R · I = V ÷ R · R = V ÷ I · P = V × I
Example: Solve for V — Current 10A, Resistance 24Ω → V = 240V · Power = 2400W
Parallel Resistance Calculator
Total resistance for identical resistors wired in parallel. Enter resistance value, number of resistors and optional voltage.
R_total = R ÷ N (identical resistors)
Example: 3 × 10Ω in parallel = 10÷3 = 3.33ΩTotal resistance is always less than the smallest individual resistor.
Airflow / Ventilation Calculator
CFM and L/s airflow through a rectangular duct from duct dimensions and air velocity. Used for HVAC design and fan sizing.
CFM = Duct area (ft²) × Velocity (ft/min)
Duct area = (W × H) ÷ 144 (inches² → ft²)
Example: 10" × 8" duct at 700 ft/min → Area = 0.556 ft² → 389 CFM (184 L/s)Velocity guide: Supply air: 600–900 ft/min · Return air: 400–600 ft/min · Exhaust: 500–800 ft/min
Tiling
3 toolsTile Estimator
Number of tiles for any room area. Supports standard and custom tile sizes. Includes waste allowance.
Tiles = (Area ÷ Tile area) × Waste factor
Always round up to full boxes. Order 10–15% extra for future repairs.
Grout Calculator
Kilograms of grout needed based on tiled area, tile size, joint width and tile thickness.
kg/m² ≈ (Joint width × Tile thickness) ÷ (Tile area × 4000)
Includes 10% waste. Always mix grout consistently and seal porous grout after curing.
Tile Adhesive Calculator
Kilograms of tile adhesive for a given area based on tile type and substrate. Includes waste factor.
Plumbing
2 toolsPipe Fall Calculator
Fall distance and gradient for a drainage pipe. Enter pipe length and fall ratio (e.g. 1:80). Checks AS/NZS 3500 minimums.
Fall = Length ÷ Ratio
Minimum falls: DN40–DN65 = 1:40 · DN80 = 1:60 · DN100 = 1:60 · DN150 = 1:150
Water Pressure Calculator
Hydrostatic pressure from pipe height. Converts between kPa, psi and bar. Checks AS/NZS 3500 limits.
Pressure (kPa) = Height (m) × 9.81
Residential: 100–500 kPa · 1 bar = 100 kPa = 14.5 psi
Solar
4 toolsSolar System Size
Recommended solar system size from daily energy use and peak sun hours. Estimates panel count and roof area.
System kW = Daily kWh ÷ (Sun hours × Efficiency)
Solar Panel Count
Number of panels and roof area for a given system size. Enter system kW and panel wattage.
Panels = System kW × 1000 ÷ Panel watts
Roof area includes 25% clearance around panels for access and cooling.
Solar Savings & Payback
Annual savings and payback period from system size, installation cost, electricity rate and feed-in tariff.
Annual generation ≈ kW × 4.5 sun hrs × 365 × 0.85
Solar Inverter Sizing
Minimum inverter size from panel capacity. Checks panel-to-inverter ratio against AS/NZS 4777.1 limits.
Quoting & Business
2 toolsJob Quote Calculator
Labour + materials quote with GST. Enter hourly rate, hours and material cost to get a total quote.
Quote = (Hours × Rate) + (Materials × Markup) + GST
Always provide itemised quotes in writing. Include call-out fee, waste disposal and any after-hours rates separately.
Markup & Discount Calculator
Selling price from cost + markup %, or discounted price from RRP. Supports tax inclusion.
Selling = Cost × (1 + Markup%) · Margin = Profit ÷ Sell
A 25% markup gives a 20% margin — markup is always higher than the equivalent margin.