FORMULA VERSION 1.0.0

Follow the quantity.

Each estimate follows the same order: normalize measurements, calculate physical geometry, apply your material assumptions, then round the final purchase package. Changing display units keeps the underlying physical quantity.

Units and input

Internal geometry uses metres, square metres and cubic metres. One international foot is exactly 0.3048 metres; an inch is 0.0254 metres. One US liquid gallon is 3.785411784 litres; one Imperial gallon is 4.54609 litres. These definitions follow the NIST Guide to SI conversion factors.

Measurements may include decimals, fractions or explicit suffixes, such as 12 ft + 7 3/8 in. A decimal comma such as 1,5 is accepted. An ambiguous comma such as 1,234 must be replaced with an unambiguous decimal point or a number without thousands separators. Invalid, non-finite, negative material dimensions and zero package sizes are rejected.

Room geometry

For a rectangular room: floor = length × width; perimeter = 2 × (length + width); gross walls = perimeter × height. Net wall area subtracts each counted door and window once. A flat ceiling equals the floor area. Irregular walls, slopes, trims and framing are outside this geometry.

Concrete, paint, tile and flooring

• Concrete volume is the shape’s area × thickness or height. Combined additional volume is added before the identical-pour multiplier. Bag count uses the product’s mixed yield, rather than dry bag weight.
• Paint volume uses net paintable area × coats ÷ the product’s per-coat coverage. Paint and optional one-coat primer remain separate. A default coverage is an example assumption, not a product recommendation.
• Flooring boxes use allowance-adjusted area ÷ coverage per box. Cost uses your entered box price and excludes tax, delivery, accessories and labor.
• Tile count uses an approximate module of (tile length + joint) × (tile width + joint). It does not optimize a cutting pattern. Whole boxes use the original unrounded area requirement.

Drywall, masonry, loose materials and boards

• Drywall counts area for your chosen layers and ceiling selection, then divides by the actual panel area. Brick and block use actual face size plus one stated joint module; openings must be removed before direct-area input.
• Gravel volume uses depth and area. Mass requires your entered bulk density in kg/m³. A volume bag and a mass bag use different purchase calculations.
• Board feet are a lumber volume measure: thickness in inches × width in inches × length in feet ÷ 12, multiplied by count. Nominal sizes are not silently converted to actual sizes.
• Deck boards use repeated board-width and gap spacing, with the first and last edge checked. Whole stock pieces per row are rounded before the chosen extra-piece allowance; this is not a fastening or cutting design.

Stairs, ramps and roofing

• Stairs use your target riser height to choose a whole number of equal risers. The upper landing provides the last tread. The rise/run layout diagonal is not a stringer cut length.
• Ramp slope = rise ÷ horizontal run. Percent, ratio and angle describe the same geometry; a flat ramp has zero percent and no finite rise-to-run ratio. No accessibility or safety compliance is certified.
• Roof projection converts by √(1 + (rise/run)²). True measured roof area skips that conversion. Bundles require your stated coverage. Multiple pitches, hips, valleys, penetrations and ridge products need separate measured quantities.

Allowances and rounding

Required material = measured quantity × (1 + allowance / 100). Purchase packages = round up(required material ÷ product package quantity). The interface may round displayed decimals; calculations retain full precision. A small floating-point boundary tolerance prevents a mathematically exact package count from becoming one extra package.

Estimated extra = purchased quantity − allowance-adjusted requirement. This is a coverage estimate; offcuts may not be reusable. Flooring and tile in Project Lite are alternatives, rather than a combined order.

Review and limits

Tests use independently calculated examples, including a 12 × 15 × 9 ft room with 61 ft² of openings (425 ft² net walls) and a 15 × 10 ft concrete slab, 4 in thick, with 10% allowance and 0.45 ft³/bag (123 bags). Formula changes require regression checks before release.

These tools estimate materials. They do not determine structural adequacy, mix design, loading, legal compliance, site safety or a contractor’s quote. Verify dimensions and product specifications before ordering.

Report a reproducible discrepancy to buildercalculator0804@gmail.com.