Shared approach
RoxyCalc accepts the units shown beside each input and converts compatible measurements before applying a material-specific formula. The result is then rounded to the next whole purchasable item where a sheet, pack, box, bag, board, or container count is required. A planning default is always a disclosed calculator choice; product instructions take priority.
Optional price fields are applied only after quantity rounding, so a price can never change the material quantity. The core calculation uses the measurements and options entered in the browser; it does not depend on an account, saved project, supplier catalogue, or live product price.
Fastener calculator
Purpose: estimate fasteners at support intersections for repeated sheets, boards, or panels.
Inputs and units: sheet length/width plus support and fastener spacing in supported metric or imperial length units; quantity and optional allowance.
supports crossed × fasteners per support × quantity × (1 + allowance)Rounding: fasteners and optional packs round up. Limit: it is not a fastening schedule or corrosion specification. Example: a 2.4 m × 1.2 m sheet over 450 mm supports with 200 mm fastener spacing produces a repeatable intersection estimate.
Sheet count calculator
Purpose: compare area division with a simple row layout.
Inputs and units: area length/width, sheet length/width, stagger choice, and optional allowance.
max(area ÷ sheet area, rows × sheets per row) + stagger allowanceRounding: the higher count and allowance round up to whole sheets. Limit: this does not optimise individual offcuts. Example: a narrow room can need more sheets by rows than area alone suggests.
Paint calculator
Purpose: estimate coating volume from paintable area, coats, and product coverage.
Inputs and units: room or surface dimensions, opening deductions, coats, coverage, and container size.
(gross area − openings) × coats ÷ coverageRounding: the displayed volume is converted to whole containers. Default: no product coverage is assumed; enter the label value. Limit: primer and separate coating systems need separate estimates.
Concrete calculator
Purpose: convert selected slab, trench, hole, or pier dimensions into volume and a bag count.
Inputs and units: relevant length, width, depth, diameter, count, bag yield, and allowance.
project volume × (1 + allowance) ÷ entered bag yieldRounding: bags round up. Default: bag yield is an estimate unless you enter the manufacturer value. Limit: it does not design reinforcement, excavation, or a structural pour.
Flooring calculator
Purpose: convert room area and pack coverage into packs.
Inputs and units: room length/width, layout pattern, pack coverage, allowance, and optional owned packs.
room area × (1 + waste) ÷ pack coverageRounding: pack count rounds up before owned whole packs are deducted. Defaults: pattern choices supply RoxyCalc planning allowances when blank. Limit: check product installation requirements and keep matching spare material when useful.
Bulk material calculator
Purpose: convert a rectangular area and depth into an order volume for mulch, soil, gravel, or sand.
Inputs and units: length, width, depth, order unit, and allowance.
area × depth × (1 + allowance)Rounding: optional bags or supplier units round up. Limit: loose and compacted volume can differ; confirm supplier guidance. Example: a 12 m² bed at 75 mm deep needs 0.9 m³ before any allowance.
Tile calculator
Purpose: estimate tiles and boxes from surface, tile size, coverage, and layout.
Inputs and units: surface and tile dimensions, tiles per box or box coverage, pattern, and optional waste.
surface area ÷ tile area, then add pattern allowanceRounding: tiles and boxes round up. Defaults: blank waste uses a disclosed RoxyCalc pattern allowance. Limit: grout, adhesive, trims, niches, and exact joint layout are separate considerations.
Decking calculator
Purpose: estimate board rows and board quantity from deck size, board dimensions, gap, and direction.
Inputs and units: deck length/width, board length/width, gap, direction, allowance, and optional fastener fields.
deck width ÷ (board width + gap), then board lengths and wasteRounding: rows and boards round up. Limit: it does not design framing, spans, or structural connections.
Fence calculator
Purpose: estimate repeated bays, posts, rails, pickets, and optional concrete or fasteners for a straight run.
Inputs and units: fence length, optional gate deduction, post spacing, rail count, picket width/gap, and allowance.
bays = ceiling(effective run ÷ post spacing); posts = bays + 1Rounding: material quantities round up. Limit: corners, slopes, returns, gates, and structural post choices need their own check.
Drywall calculator
Purpose: estimate walls only using both area and simple layout counts.
Inputs and units: wall length/height/count, opening area, sheet size, orientation, allowance, and optional screw data.
use the higher of area count and simple row-layout count, then add allowanceRounding: sheets and optional screw packs round up. Limit: it does not estimate ceilings, tape, compound, offcut reuse, or a staggered-joint design.
Paver calculator
Purpose: estimate separate paver, base, and bedding quantities for a rectangular path or patio.
Inputs and units: area, paver dimensions, pattern/waste, base depth, bedding depth, and optional base compaction.
pavers: area ÷ paver area; layers: area × depthRounding: pavers and optional boxes round up. Limit: base compaction applies only to the base calculation; drainage, edge restraint, and jointing material are separate checks.
Trim calculator
Purpose: convert room perimeter and stock length into a whole-piece trim estimate.
Inputs and units: room length/width/count, optional opening deduction, stock length, allowance, and optional nail spacing.
(rectangular perimeter × rooms − deductions) × (1 + allowance) ÷ stock lengthRounding: stock lengths round up. Limit: it does not create a cut-optimisation plan for individual walls or mitres.
Accepted units and worked examples
These method notes supplement the formulas above. Compatible inputs are normalised before a material-specific calculation is made. The calculator only accepts the options displayed beside its fields.
Fastener calculator
Accepted units: panel dimensions use mm, cm, or m in metric mode and in, ft, or yd in imperial mode; spacing uses metric lengths or in/ft. Example: ten 2.4 m × 1.2 m sheets with 600 mm supports and 300 mm fastener spacing produce 25 fasteners per sheet and 275 with a 10% allowance.
Sheet count calculator
Accepted units: area dimensions use mm, cm, or m in metric mode and in, ft, or yd in imperial mode; sheet dimensions use metric lengths or in/ft. Example: a 5 m × 3 m area using 2.4 m × 1.2 m sheets, a half-sheet stagger, and 10% allowance requires 11 sheets.
Paint calculator
Accepted units: dimensions use cm/m or in/ft; deductions use m² or ft²; coverage supports square metres or square feet per litre or gallon; containers use litres or gallons. Example: a 5 m × 4 m room, 2.4 m high, less 2 m² of openings, with two coats at 12 m²/L and 10% allowance needs about 7.55 L, or two 4 L containers.
Concrete calculator
Accepted units: plan and depth dimensions use mm, cm, or m in metric mode and in/ft in imperial mode; bag size accepts kg or lb bags. Example: a 3 m × 2 m × 100 mm slab is 0.6 m³ before allowance and 0.66 m³ at 10% allowance.
Flooring calculator
Accepted units: room dimensions use cm/m or in/ft; pack coverage uses m² or ft². Example: a 5 m × 4 m room with 2.2 m² packs and the 15% diagonal planning default needs 11 packs before any owned packs are deducted.
Bulk material calculator
Accepted units: area lengths use cm/m or ft/yd; depth uses mm, cm, m, in, or ft; ordering uses litres, m³, or ft³ according to the selected system. Example: a 12 m² bed at 75 mm deep needs 0.9 m³ before any allowance.
Tile calculator
Accepted units: surface lengths use cm/m or ft; tile dimensions use mm/cm or in/ft; box coverage uses m² or ft². Example: a 5 m × 4 m floor with 600 mm square tiles, 10 tiles per box, and 10% allowance needs 62 tiles or seven boxes.
Decking calculator
Accepted units: deck lengths use cm/m or ft; board lengths use cm/m or ft; board width and gap use mm/cm or in. Example: a 5 m × 3 m deck with 140 mm boards, 6 mm gaps, 4.8 m stock, and 10% allowance needs 21 rows and 47 boards.
Fence calculator
Accepted units: run and gate lengths use cm/m or ft; post spacing, picket width, and gaps use mm/cm or in. Example: a 30 m run less a 3 m gate at 2.4 m post spacing has 12 bays and 13 posts before optional extras.
Drywall calculator
Accepted units: wall dimensions use cm/m or ft; sheet dimensions use mm/cm/m or in/ft; openings use m² or ft²; stud and screw spacing use mm/cm or in. Example: four 5 m × 2.4 m walls, less 2 m² of openings, with 2.4 m × 1.2 m sheets and 10% allowance need 22 sheets.
Paver calculator
Accepted units: patio dimensions use cm/m or ft; pavers use mm/cm or in; box coverage uses m² or ft². Example: a 5 m × 4 m patio with 400 mm square pavers, 100 mm base at 1.1 compaction, and 40 mm bedding needs 140 pavers, 2,200 L base, and 800 L bedding.
Trim calculator
Accepted units: room and stock lengths use cm/m or ft; nail spacing uses mm/cm or in. Example: two 5 m × 4 m rooms less 2 m of openings, with 2.4 m stock and 10% allowance, need 16 lengths.
What takes priority over a calculator
The exact product label and manufacturer installation instructions take priority over a generic coverage assumption. Site conditions, compaction, surface texture, substrate, drainage, structural spans, fire or wet-area requirements, local codes, supplier unit definitions, and professional advice can all change the appropriate quantity or method.
RoxyCalc does not claim that a general quantity estimate is a structural design, permit approval, engineering calculation, trade specification, or safety certification. For high-consequence work, use the calculator only as a preliminary arithmetic check and have the final plan reviewed by the right qualified person.