51 Free Construction Calculators &amp; Site Tools

Building Square Calculator

Convert m² and building squares

Compare project cost by floor area

Cost per m² Calculator

Fall & Gradient Calculator

Calculate fall, ratio and percentage

Estimate roof area from plan dimensions and pitch

Roof Area Calculator

Add or remove Australian GST

GST Calculator

Markup vs Margin Calculator

Compare markup and gross margin

Calculate cost plus builder margin and GST

Cost-Plus Calculator

CHOOSE A CATEGORY

Useful construction calculations in one place

Search or browse 51 calculators, enter the project dimensions or costs you know, then calculate. Each result is intended as a fast planning or estimating aid and can be reset and recalculated as the job changes.

Measurements

Conversions, area and volume

7 toolsOpen tools ↓

Concrete & Masonry

Concrete, bricks, blocks and retaining walls

9 toolsOpen tools ↓

Timber & Framing

Timber, framing and decking

7 toolsOpen tools ↓

Roofing & Finishes

Roofing, plaster, paint and flooring

9 toolsOpen tools ↓

Site & Levels

Slope, fall, drainage and excavation

8 toolsOpen tools ↓

Costs & GST

Margin, GST, cost-plus and project costs

11 toolsOpen tools ↓

Find a tool

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Showing 51 of 51 tools. Search understands common variations such as sqm/m², m3/m³, linear/lineal and hyphenated terms.

Measurements

Conversions, area and volume · 7 tools

m² ↔ Building Squares

Convert square metres to Australian building squares and back.

ValueConvert

Result

Building squares: 10.76 squares
Conversion used: 1 square = 9.290304 m²

Length Converter

Convert common metric and imperial construction measurements.

ValueFromTo

Result

Converted value: 1,000.000 mm

Area & Volume Calculator

Calculate rectangular floor area, perimeter and cubic volume.

Length (m)Width (m)Height / depth (m)

Result

Area: 24.00 m²
Perimeter: 20.00 m
Volume: 57.60 m³

Triangle Area Calculator

Calculate the area of a triangular section from its base and perpendicular height.

Base (m)Perpendicular height (m)

Result

Triangle area: 12.00 m²
Formula: ½ × base × height

Circle Area & Circumference

Calculate circular area and circumference from a diameter.

Diameter (m)

Result

Area: 7.07 m²
Circumference: 9.42 m

Trapezoid Area Calculator

Calculate the area of a trapezoid from its two parallel sides and perpendicular height.

Parallel side A (m)Parallel side B (m)Perpendicular height (m)

Result

Area: 15.00 m²

Right-Angle / Diagonal Calculator

Calculate the diagonal between two perpendicular set-out dimensions using Pythagoras.

Length (m)Width (m)

Result

Diagonal (metres): 7.211 m
Diagonal (millimetres): 7,211 mm

Related EBC guides

Understand the numbers before using them on site

Why site surveys matter before building →What to check before buying land to build →Building specifications explained →

Concrete & Masonry

Concrete, bricks, blocks and retaining walls · 9 tools

Concrete Slab Calculator

Estimate concrete volume for a rectangular slab, including wastage.

Length (m)Width (m)Thickness (mm)Wastage (%)

Result

Net concrete: 6.000 m³
Order quantity: 6.300 m³

Strip Footing Calculator

Estimate concrete for continuous strip footings.

Total footing length (m)Width (mm)Depth (mm)Wastage (%)

Result

Net concrete: 4.050 m³
Order quantity: 4.253 m³

Brick & Block Quantity

Estimate masonry quantities using common Australian brick formats, standard concrete blocks or a custom unit size.

Wall length (m)Wall height (m)Doors/windows (m²)Australian masonry formatMortar joint (mm)Wastage (%)

Result

Selected format: Standard brick
Net wall area: 21.00 m²
Approx. units per m²: 48.4
Units required: 1,094

Mortar Materials Calculator

Estimate total bricklaying mortar plus cement, hydrated lime and sand quantities. Default mix is M3 1:1:6. Confirm the specified mortar class before use.

Wall length (m)Wall height (m)Doors/windows (m²)Australian masonry formatMortar joint (mm)Mortar mix (Cement : Lime : Sand)Mortar/perforation allowance (%)Cement bag size (kg)Lime bag size (kg)

Result

Mix by volume: 1 cement : 1 lime : 6 sand
Net wall area: 21.00 m²
Approx. masonry units: 1,018
Mortar before allowance: 0.354 m³
Total mortar to allow: 0.442 m³
Cement to buy: 14 × 20 kg bags (≈ 262.5 kg)
Hydrated lime to buy: 5 × 20 kg bags (≈ 97.7 kg)
Sand to buy: 0.56 m³ (≈ 1.06 t damp)
Water: Add clean water gradually to reach workable consistency

Circular Pier Concrete

Estimate concrete for round bored piers or posts, including quantity and wastage.

Pier diameter (mm)Pier depth (m)Number of piersWastage (%)

Result

Concrete per pier: 0.191 m³
Net concrete: 1.527 m³
Order quantity: 1.603 m³

Retaining Wall Block Quantity

Estimate block quantity from wall face area. Structural design, footing and drainage are separate checks.

Wall length (m)Average wall height (m)Block face length (mm)Block face height (mm)Wastage (%)

Result

Wall face area: 10.00 m²
Blocks required: 135

Premix Concrete Bag Calculator

Estimate premix concrete bag quantity from required volume and the manufacturer yield per bag.

Concrete required (m³)Yield per bag (L)Wastage (%)

Result

Volume incl. allowance: 262.5 L
Bags required: 27
Yield used: 10.0 L per bag

Block Core-Fill Concrete

Estimate core-fill concrete from block quantity and the fill rate for the selected masonry product.

Blocks to core-fillFill rate (L/block)Wastage (%)

Result

Net core fill: 0.750 m³
Order volume: 0.788 m³
Order litres: 788 L

Masonry Mortar Bag Quantity

Estimate bag quantity using the wall area and the manufacturer or supplier coverage rate for the chosen mortar.

Masonry area (m²)Coverage per bag (m²)Wastage (%)

Result

Area incl. wastage: 44.00 m²
Bags required: 44

Related EBC guides

Understand the numbers before using them on site

Soil testing before a new home or extension →Site costs: soil, excavation, rock and access →Retaining walls for homes and extensions →

Timber & Framing

Timber, framing and decking · 7 tools

Wall Stud Quantity

Estimate regular studs along a straight wall. Extra studs at corners/openings are not included.

Wall length (m)Stud spacingExtra allowance (%)

Result

Base studs: 15
With allowance: 17

Decking Board Calculator

Estimate board rows and total lineal metres for a rectangular deck.

Board run length (m)Deck width (m)Board width (mm)Gap (mm)Wastage (%)

Result

Board rows: 43
Net lineal metres: 215.00 lm
Order allowance: 236.50 lm

Joist Quantity

Estimate regularly spaced joists and total lineal metres.

Width across joists (m)Joist length (m)Spacing

Result

Joists: 10
Total lineal metres: 50.00 lm

Noggin Quantity

Estimate regular noggins between studs for a straight wall. Corners, openings and special framing are separate.

Wall length (m)Stud spacingNoggin rowsExtra allowance (%)

Result

Stud bays: 14
Base noggins: 28
With allowance: 31

Lineal Metres → Timber Pieces

Convert required lineal metres into stock-length timber pieces with a cutting allowance.

Required lineal metresStock length per piece (m)Cutting / wastage (%)

Result

Required incl. allowance: 93.50 lm
Pieces to order: 18
Purchased lineal metres: 97.20 lm

Decking Screw Quantity

Estimate fixing quantity from deck dimensions, board pitch, joist spacing and screws per board/joist crossing.

Board run length (m)Deck width (m)Board width (mm)Board gap (mm)Joist spacing (mm)Screws per crossingExtra allowance (%)

Result

Board rows: 43
Joist lines: 13
Base screw quantity: 1,118
With allowance: 1,174

Batten / Member Spacing Quantity

Estimate the number of regularly spaced battens, members or set-out points across a measured run.

Run length (m)Spacing (mm)

Result

Spaces: 14
Members incl. both ends: 15

Related EBC guides

Understand the numbers before using them on site

The Victorian home building process →Building specifications explained →Building inclusions to decide early →

Roofing & Finishes

Roofing, plaster, paint and flooring · 9 tools

Roof Area & Pitch

Approximate a simple roof area from plan dimensions and pitch.

Plan length (m)Plan width (m)Roof pitch (degrees)Eave allowance each side (m)

Result

Plan area incl. eaves: 114.81 m²
Approx. roof surface: 124.27 m²

Plasterboard Sheet Calculator

Estimate plasterboard sheets from combined wall and ceiling area.

Wall area (m²)Ceiling area (m²)Sheet sizeWastage (%)

Result

Total lining area: 180.00 m²
Sheets required: 69

Paint Calculator

Estimate paint litres from area, coverage rate and number of coats.

Paintable area (m²)Number of coatsCoverage (m²/L per coat)Wastage (%)

Result

Net paint: 21.43 L
Order allowance: 23.57 L

Flooring & Tile Quantity

Calculate purchase area and optional carton/box quantity.

Floor area (m²)Wastage (%)Coverage per box (m²)

Result

Purchase area: 60.50 m²
Boxes required: 28

Roofing Sheet Quantity

Estimate sheet count for simple equal roof planes using effective sheet cover width.

Roof length along eave (m)Sheet / slope length (m)Equal roof planesEffective sheet cover (mm)Extra sheets (%)

Result

Sheets per plane: 16
Base sheet count: 32
Order quantity: 34
Approx. sheet lineal metres: 170.00 lm

Cornice / Skirting Length

Calculate room perimeter lineal metres with an optional opening deduction.

Room length (m)Room width (m)Measure forOpening deduction (m)Wastage (%)

Result

Net lineal metres: 17.10 lm
Order allowance: 18.81 lm

Room Wall Area

Calculate gross and net internal wall area for paint, plasterboard or other wall finishes.

Room length (m)Room width (m)Wall height (m)Doors/windows total (m²)

Result

Gross wall area: 48.60 m²
Opening deduction: 4.00 m²
Net wall area: 44.60 m²

Insulation Pack Calculator

Estimate insulation purchase area and packs from the coverage printed on the product pack.

Area to insulate (m²)Coverage per pack (m²)Wastage (%)

Result

Purchase area: 126.00 m²
Packs required: 11
Pack coverage used: 11.60 m²

Rafter Length & Roof Rise

Estimate common-rafter slope length and roof rise from horizontal run and roof pitch.

Horizontal run to ridge (m)Roof pitch (degrees)Horizontal eave overhang (m)

Result

Rise to ridge: 1.657 m
Rafter slope length incl. overhang: 4.817 m

Related EBC guides

Understand the numbers before using them on site

Building inclusions to decide early →Building specifications explained →Energy-efficient home design in Victoria →

Site & Levels

Slope, fall, drainage and excavation · 8 tools

Fall / Gradient Calculator

Calculate required fall in millimetres from a 1:X gradient.

Run length (m)Gradient 1 : X

Result

Required fall: 120.0 mm
Gradient: 1:100

Slope % ↔ Ratio ↔ Degrees

Convert a percentage gradient to 1:X ratio and degrees.

Slope (%)

Result

Ratio: 1:50.00
Angle: 1.15°

Excavation & Spoil Volume

Estimate in-situ excavation and a loose-spoil allowance.

Length (m)Width (m)Average depth (m)Loose spoil increase (%)

Result

In-situ volume: 25.00 m³
Loose spoil allowance: 31.25 m³

Tank Capacity

Estimate rectangular or cylindrical tank capacity in litres.

Tank shapeLength (m) — rectangularWidth (m) — rectangularDiameter (m) — cylinderWater height (m)

Result

Capacity: 4,000 L
Volume: 4.000 m³

Soil m³ ↔ Tonnes

Convert soil volume and mass using an adjustable bulk density.

ValueConvertBulk density (t/m³)

Result

Estimated mass: 16.00 t
Density used: 1.60 t/m³

RL / Level Difference

Compare two reduced levels and calculate the rise or fall over a horizontal run.

Start RL (m)End RL (m)Horizontal run (m)

Result

Level change: -150.0 mm
Direction: Fall
Gradient: -1.500%
Approx. ratio: 1:66.67

Rainwater Collection

Estimate roof runoff captured from a rainfall event. One millimetre of rain on one square metre equals one litre before losses.

Effective roof area (m²)Rainfall event (mm)Collection efficiency (%)

Result

Gross roof runoff: 4,500 L
Estimated collected water: 4,050 L
Collection efficiency: 90%

Cut & Fill Volume

Estimate simple cut and fill volumes from plan area and average depth, then compare the balance.

Cut area (m²)Average cut depth (m)Fill area (m²)Average fill depth (m)

Result

Cut volume: 32.00 m³
Fill volume: 18.00 m³
Approx. surplus cut: 14.00 m³

Related EBC guides

Understand the numbers before using them on site

Building on a sloping block in Melbourne →Stormwater and drainage planning →Site costs explained →

Costs & GST

Margin, GST, cost-plus and project costs · 11 tools

GST Calculator

Add or remove Australian GST at 10%.

Amount ($)Amount entered is

Result

Ex GST: $10,000.00
GST: $1,000.00
Inc GST: $11,000.00

Markup vs Margin

Calculate sell price using either markup on cost or gross margin on sell price.

Cost ($)MethodPercentage (%)

Result

Sell price ex GST: $12,000.00
Gross profit: $2,000.00
Actual margin: 16.67%

Cost-Plus Calculator

Apply a builder fee percentage to project cost, then calculate GST.

Project cost ex GST ($)Builder fee on cost (%)

Result

Builder fee: $20,000.00
Total ex GST: $120,000.00
GST: $12,000.00
Total inc GST: $132,000.00

Cost per m² / Building Square

Compare a total project cost against floor area.

Project cost ($)Floor area (m²)

Result

Cost per m²: $2,500.00
Building squares: 21.53 squares
Cost per square: $23,225.76

Progress Payment / Variation

Calculate a percentage claim or variation amount from an ex-GST base.

Base amount ex GST ($)Claim / variation (%)

Result

Amount ex GST: $20,000.00
GST: $2,000.00
Amount inc GST: $22,000.00

Project Contingency

Add a contingency allowance to an ex-GST project budget.

Base budget ex GST ($)Contingency (%)

Result

Contingency allowance: $25,000.00
Budget incl. contingency ex GST: $275,000.00
Budget incl. GST: $302,500.00

Labour Cost Calculator

Estimate labour cost from crew size, hours, days and hourly rate.

WorkersHours per worker / dayDaysHourly rate ex GST ($)

Result

Total labour hours: 80.0 h
Labour cost ex GST: $5,200.00
Labour cost inc GST: $5,720.00

Retention Calculator

Calculate a simple retention amount and payable balance from a claim value.

Claim amount ex GST ($)Retention rate (%)

Result

Retention withheld: $2,500.00
Payable ex GST: $47,500.00
Payable inc GST: $52,250.00

Markup ↔ Margin Percentage

Convert a markup percentage on cost to gross margin percentage on sell price, or the other way around.

Percentage (%)Convert

Result

Markup on cost: 20.00%
Equivalent gross margin: 16.67%

Hourly ↔ Day Rate

Convert an ex-GST hourly trade rate to a day rate, or a day rate back to an hourly rate.

Rate ex GST ($)Hours per dayConvert

Result

Day rate ex GST: $600.00
Day rate inc GST: $660.00

Price Escalation / Adjustment

Apply a percentage increase to an ex-GST amount and show the revised ex-GST and inc-GST totals.

Original amount ex GST ($)Increase (%)

Result

Adjustment: $5,000.00
Revised ex GST: $105,000.00
Revised inc GST: $115,500.00

Related EBC guides

Understand the numbers before using them on site