Square Footage Calculator
Calculate square footage for common shapes, then include deductions, waste, package coverage, material cost, and tax in one order estimate.| Measure | Value | Use | Copy |
|---|---|---|---|
| {{ row.measure }} | {{ row.value }} | {{ row.use }} |
Ordering notes
Measurement path
{{ values.shape_label }} uses {{ values.formula_label }}. The calculator repeats that one-shape area {{ formatInteger(values.quantity) }} time{{ values.quantity === 1 ? '' : 's' }} before deductions.
Adjustment path
{{ displaySqft(values.deducted_area_sqft) }} is deducted, then {{ formatNumber(values.waste_percent, 1) }}% adds {{ displaySqft(values.waste_area_sqft) }}. Waste guidance must come from the actual material and installation method.
Purchase boundary
The {{ displaySqft(values.order_area_sqft) }} target rounds to {{ formatInteger(values.package_count) }} whole packages covering {{ displaySqft(values.purchased_coverage_sqft) }}.
Package rounding is off, so purchased coverage equals the waste-adjusted order area.
Verify before buying
Confirm irregular edges, alcoves, openings, unusable offcuts, product coverage, batch or lot constraints, returns, labor, accessories, and local tax before placing an order.
Introduction:
Measured area and purchased coverage answer different questions. A room may contain 100 square feet of floor, yet the order can be larger after deductions, cutting waste, repeated spaces, and whole-box rounding are applied. Keeping those stages separate makes it easier to find where an estimate grew.
Square footage is two-dimensional surface area expressed in square feet. Length units must be converted before they are multiplied: converting 4 metres to feet and 3 metres to feet produces the same physical area as calculating 12 square metres and converting the result. Mixing an unconverted metre value with a foot value does not.
| Shape | Measurements that matter | Common mistake |
|---|---|---|
| Rectangle or square | Two perpendicular sides | Using wall-to-wall plans when the finished surface stops earlier |
| Circle | Radius, or diameter divided by two | Using the diameter as though it were the radius |
| Triangle | Base and perpendicular height | Using a sloped edge for the height |
| Trapezoid | Two parallel widths and their perpendicular separation | Averaging sides that are not parallel |
| L-shape | Two non-overlapping rectangles | Counting an overlap twice or leaving a gap |
Deductions remove known openings or excluded surfaces from the repeated gross area. Waste allowance is applied after that subtraction because offcuts and pattern losses relate to the material-covered area. Package coverage then rounds the order upward to a purchasable quantity, and cost uses that purchased coverage rather than the unrounded measurement.
Area alone cannot judge layout efficiency, direction changes, pattern matching, damaged pieces, batch matching, or irregular boundaries. Measure the finished surface, follow the material manufacturer's allowance guidance, and keep enough surplus for repairs when matching the product later may be difficult.
How to Use This Tool:
Break the project into simple non-overlapping surfaces before entering measurements.
- Choose Area shape and enter the required perpendicular measurements with the correct units. Use Known area only when a reliable plan or measurement already supplies the surface area.
- Set Quantity when the same shape repeats. For different shapes or sizes, calculate them separately and add the net areas.
- Enter any fixed deduction, then choose a waste percentage that matches the material, pattern, room shape, and installer guidance.
- Add package coverage when the product is sold by box, roll, pallet, or another fixed unit. Leave it at zero for an area-only estimate.
- Enter cost per square foot and tax only when a budget estimate is needed. Read the sequence from repeated gross area through purchased coverage before trusting the total.
Interpreting Results:
Net area is the repeated shape area after the deduction. Order area adds waste. Purchased coverage rounds that order to complete packages when package coverage is present. The surplus is purchased coverage minus order area, not necessarily a count of reusable full pieces.
- A deduction cannot exceed repeated gross area; correct the shape, quantity, units, or deduction when that warning appears.
- An exact package boundary does not add an extra package. Any positive remainder does.
- For irregular land, legal boundaries, or construction documents, use survey or plan data appropriate to the decision rather than a rough tape measurement.
Technical Details:
Each selected shape is reduced to square feet before quantity, deductions, waste, package rounding, and cost are applied. Geometry uses full floating-point precision; formatting rounds only what is shown.
Formula Core:
The supported shape identities are:
| Shape | Area rule |
|---|---|
| Rectangle or square | length × width |
| Circle | π × radius²; entered diameter is divided by 2 first |
| Triangle | base × perpendicular height ÷ 2 |
| Trapezoid | (parallel width A + parallel width B) × perpendicular height ÷ 2 |
| L-shape | section A rectangle + section B rectangle |
| Known area | entered area converted directly to ft² |
After the single-shape area is known, the material-order sequence is fixed.
When package coverage is positive, count rounds upward and purchased coverage becomes the cost basis. Without package coverage, order area is the cost basis.
Unit rules:
Length inputs support metres, centimetres, feet, inches, and yards. Known areas, deductions, and package coverage support square metres, square centimetres, square feet, square inches, square yards, acres, and hectares. One square foot equals exactly 0.09290304 square metre under the international foot definition.
Quantity must be a whole number from 1 through 10,000. Waste is accepted from 0% through 75%, tax from 0% through 30%, and the deduction may equal but not exceed repeated gross area. Package rounding uses a tiny tolerance so an exact arithmetic boundary is not pushed into an extra package by floating-point noise.
Worked Examples:
Circular area with whole-box ordering
Two circles with a 6 ft radius have 226.19 ft² of repeated gross area. Deducting 10 ft² leaves 216.19 ft²; adding 5% waste raises the order to 227.00 ft². At 20 ft² per package, the count rounds to 12 and purchased coverage becomes 240 ft². A $3 per ft² price and 8.25% tax produce a $779.40 total.
References:
- SI Units – Area, National Institute of Standards and Technology.
- NIST Guide to the SI, Appendix B.8 conversion factors, National Institute of Standards and Technology.