Square Footage Calculator

Area shape:

Pick the geometry model for the surface you measured.

Measurement system:

Use imperial for feet/inches/yards or metric for meters/centimeters.

Dimension unit:

Choose the unit used by the length, width, radius, base, or height fields below.

Length:

Measure the finished surface length.

Width:

Measure the finished surface width.

Circle measure:

Choose whether the circular dimension is radius or diameter.

{{ circleMeasureLabel }}:

Measure the circular patio, room, rug, planting bed, or panel.

Base:

Measure the triangle base.

Height:

Use the perpendicular height, not a sloped side.

Top width:

Measure the first parallel side.

Bottom width:

Measure the second parallel side.

Trapezoid height:

Use the straight height between the parallel sides.

Section A length:

Break the L-shape into two non-overlapping rectangles.

Section A width:

Use the paired width for section A.

Section B length:

Measure only the second non-overlapping rectangle.

Section B width:

Use the paired width for section B.

Measured area:

Enter the known area before quantity, deductions, or waste.

Quantity:

Use 1 for a single area, or increase for repeated identical shapes.

area(s)

Waste allowance:

Add project waste for material ordering; the raw square footage stays visible in the takeoff.

Cost per square foot:

Optional budget estimate using square-foot pricing.

$ / sq ft

Check square footage inputs

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Deducted area:

Optional area to subtract after quantity is applied.

Package coverage:

Leave 0 when you only need square footage and cost by area.

sq ft / package

Tax rate:

Leave 0 for a pre-tax material estimate.

Line	Value	Detail	Copy
{{ row.line }}	{{ row.value }}	{{ row.detail }}

Waste	Order area	Packages / cost	Buying note	Copy
{{ row.waste }}	{{ row.orderArea }}	{{ row.purchase }}	{{ row.note }}

Check	Status	Reason	Copy
{{ row.check }}	{{ row.status }}	{{ row.reason }}

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Square footage is the surface area behind many home, shop, landscape, and planning estimates. A room, patio, wall panel, planting bed, rug, deck section, or floor layout can all start with the same question: how much surface is there before waste, deductions, package rounding, or price?

This calculator turns common shape measurements into square feet, then carries the result into quantity and buying checks. It supports rectangles and squares, circles, triangles, trapezoids, an L-shape split into two rectangles, and a measured-area entry when a drawing or takeoff already gives the area.

The result is not only the bare geometric area. The estimate can multiply identical areas, subtract obstructions or uncovered sections, add a waste allowance, round coverage up to whole packages, and apply an optional cost per square foot plus tax. That makes it useful for checking a shopping list, quote note, or project worksheet before ordering material.

The geometric square footage stays visible while quantity, deductions, waste allowance, package rounding, and optional cost build the order estimate.

Treat the number as an estimate, not a replacement for field judgment. Out-of-square rooms, curved edges, product layout direction, unusable offcuts, code rules, installation method, delivery constraints, and supplier minimums can all change what should be ordered.

Technical Details:

The calculator converts visible dimensions to feet before applying the selected geometry formula. Imperial length entries can use feet, inches, or yards. Metric length entries can use meters or centimeters. A measured-area entry can use square feet, square inches, square yards, acres, square meters, or hectares, then converts that known area to square feet.

Every valid shape produces an area per shape. Quantity multiplies that area for repeated identical spaces. Deducted area is subtracted after quantity, then capped so net area cannot go below zero. Waste allowance is applied to net area, and package coverage rounds the purchase estimate up only when a positive square-foot coverage per package is entered.

Formula Core:

The formulas use the dimensions after unit conversion. The L-shape model assumes two non-overlapping rectangles, so the shared corner should not be counted twice.

\begin{matrix} A_{rectangle} & = & L \times W \\ A_{circle} & = & π \times r^{2} \\ A_{triangle} & = & \frac{b \times h}{2} \\ A_{trapezoid} & = & \frac{(a + b) \times h}{2} \\ A_{L-shape} & = & (L_{A} \times W_{A}) + (L_{B} \times W_{B}) \\ A_{order} & = & (A_{shape} \times Q - D) \times (1 + \frac{W}{100}) \end{matrix}

Square footage formula variables and meanings
Symbol	Meaning	Result field affected
L and W	Rectangle length and width after conversion to feet.	Area per shape and Formula used
r	Circle radius in feet. If diameter is entered, half of that value becomes the radius.	Area per shape
a, b, and h	Trapezoid parallel widths and perpendicular height.	Formula used and Measurement Checks
Q	Quantity of identical areas, rounded to a whole count of at least one.	Repeated area
D	Deducted square footage for obstructions, openings, islands, or uncovered sections.	Net square footage
W	Waste allowance, limited to 0% through 75%.	Waste allowance area and Order area

When package coverage is entered, the package count is rounded upward with a ceiling rule. Purchased coverage equals whole packages times square feet per package, and surplus is the coverage left after the order area is met. If package coverage is left at 0, the cost basis uses the exact order area instead of whole-package coverage.

Square footage validation rules
Input or setting	Required condition	Correction cue
Shape dimensions	Required lengths, widths, radius, base, height, or measured area must be greater than zero.	Correct the visible measurement before reading takeoff rows.
Quantity	At least 1 area.	Use 1 for a single area, or a whole count for repeated matching areas.
Waste allowance	0% to 75%.	Use 0% for geometry only, or add a project allowance before ordering material.
Cost and package inputs	Cost per square foot, deducted area, and package coverage cannot be negative.	Set unused optional fields to 0.
Tax rate	0% to 30%.	Use 0% when only pre-tax material cost matters.

The output also converts the order area to square yards, square meters, acres, and hectares. These conversions help compare labels, plans, and land-area references, but the main purchase math still starts from the square-foot order area shown in the summary and takeoff table.

Everyday Use & Decision Guide:

Start with the shape that best matches the surface you measured. Use a rectangle for most rooms and panels, a circle for round patios or beds, a triangle for half-rectangle sections, and a trapezoid when two opposite sides are parallel. Use L-shape only when the layout can be split into two rectangles that do not overlap.

Set Measurement system before entering numbers so the visible units match the tape, plan, or product sheet. Switching systems converts current values, which is useful for checking metric plans against square-foot pricing, but it also means the displayed values should be reviewed after the switch.

Area Takeoff is the audit trail. It shows the formula used, area per shape, repeated area, deducted area, net square footage, waste area, order area, conversions, package rounding, and estimated cost.
Waste Scenarios compares 0%, 5%, 10%, 15%, 20%, and the entered allowance so nearby waste choices are easy to compare.
Area Order Ladder charts the same waste scenarios and adds purchased coverage when package coverage is entered.
Measurement Checks explains formula choice, unit handling, deductions, package rounding, cost basis, and when irregular layouts should be split into smaller shapes.
JSON keeps the exact inputs, computed outputs, scenarios, and check rows together for a record or handoff note.

Use Deducted area for fixed portions that will not receive the material, such as an island footprint, permanent cabinet run, wall opening, or excluded section. The calculator subtracts the deduction after quantity is applied, so a single deduction should represent the total amount to remove from the repeated area.

Use Waste allowance when the square footage will become a material order. Cuts, mistakes, color or pattern matching, breakage, and future repair stock can all require more than the exact geometric area. The calculator does not decide the correct allowance for a product, so compare the result with the package instructions, supplier guidance, and installer takeoff.

The clearest buying check is the gap between Order area and Purchased coverage. A small surplus may still be acceptable for a simple rectangular surface, but it deserves a closer look when the layout has many cuts, diagonal pieces, curves, or products that must match by lot.

Step-by-Step Guide:

Use this sequence when you want a square-footage estimate that can be checked against a quote, product label, or project worksheet.

Choose Area shape. If the layout is irregular, split it into supported shapes and run each section separately, or use Measured area when a plan already gives the total.
Set Measurement system and Dimension unit. Confirm that length fields show the units you measured.
Enter the required dimensions. For triangles and trapezoids, use the perpendicular height, not a sloped side.
Enter Quantity for repeated identical rooms, panels, plots, or sections.
Set Waste allowance. Use 0% for exact area math, or enter the material allowance you want included in Order area.
Enter Cost per square foot only when a material budget estimate is useful. Leave it at 0 for area-only results.
Open Advanced when you need Deducted area, Package coverage, or Tax rate.
Read Area Takeoff first, then compare nearby allowances in Waste Scenarios and Area Order Ladder.
If the summary says Check square footage inputs, correct the listed input error before using the result.

A complete pass ends with the shape formula, net area, order area, any whole-package count, surplus coverage, and optional material cost all visible in one estimate.

Interpreting Results:

Area per shape is the pure geometry result for one selected shape. Repeated area applies quantity. Net square footage subtracts any advanced deduction. Order area adds the entered waste allowance and is the main value to compare with material coverage.

Formula used shows the converted-foot values behind the square-foot result.
Waste allowance area is the extra square footage added to net area, not a separate surface.
Package rounding appears only when package coverage is greater than zero.
Purchased coverage can exceed order area because partial packages are rounded up.
Estimated cost uses purchased coverage when package rounding is active, otherwise it uses the exact order area.
Square yards, square meters, acres, and hectares are conversions of the order area.

Do not read surplus as a guarantee that every leftover piece will be useful. Offcuts may be too short, directional, damaged, or needed for future repairs. For land, permit, or real-estate uses, confirm the measurement method required by the relevant authority or professional standard.

Worked Examples:

Default rectangle with waste and cost

A 12 ft by 10 ft rectangle has an area per shape of 120.00 sq ft. With quantity 1, no deduction, and 10% waste, Order area becomes 132.00 sq ft. At $3.50 per sq ft and no package rounding or tax, the estimated cost is $462.00.

L-shaped room with a deduction

An L-shape entered as section A 16 ft by 10 ft and section B 8 ft by 6 ft gives 160.00 sq ft plus 48.00 sq ft, or 208.00 sq ft before adjustments. If a built-in cabinet area of 12 sq ft is deducted, net square footage becomes 196.00 sq ft. A 15% waste allowance raises the order area to 225.40 sq ft.

Package coverage changes the purchase area

For a 225.40 sq ft order area with packages that cover 23.50 sq ft each, the exact count is about 9.591 packages. The calculator rounds up to 10 packages, so purchased coverage becomes 235.00 sq ft and surplus is 9.60 sq ft. If cost per square foot is entered, cost uses 235.00 sq ft because that is the purchased coverage.

Measured metric area converted to square feet

A measured area of 20 sq m converts to about 215.28 sq ft before quantity, deductions, or waste. With quantity 2 and 5% waste, the order area is about 452.08 sq ft. The takeoff rows also show square yards, acres, and hectares so the same estimate can be compared across different unit conventions.

Input check before a result

If circle radius is 0, triangle height is missing, quantity is 0, or waste exceeds 75%, the summary changes to Needs input and the result tables show the correction message. Fix the required measurement or allowed range first; cost and export outputs are only meaningful after the area inputs are valid.

FAQ:

Which shape should I choose for an irregular room?

Split the room into simple supported shapes and calculate each section, then add the results. Use the L-shape option only when two non-overlapping rectangles describe the layout cleanly.

Does the calculator subtract openings automatically?

No. Enter any obstruction, opening, island, or excluded area in Deducted area. The deduction is applied after quantity and before waste.

Why is purchased coverage higher than order area?

Package coverage rounds the estimate up to whole packages. The extra coverage is shown as surplus so the rounding effect is visible.

Can I use 0% waste?

Yes. Use 0% when you only need geometric square footage. Add a waste allowance when the result will guide a material order with cuts, breakage, layout loss, or repair stock.

What does estimated cost include?

It includes cost per square foot times the cost basis, plus the entered tax rate. It does not include labor, delivery, adhesive, fasteners, underlayment, disposal, permits, or related job materials.

Are the calculations performed from the values on the page?

Yes. The visible calculation runs in the browser from the entered measurements and settings. The CSV, chart image, document, and JSON outputs are based on the visible estimate data.

Glossary:

Square footage: The area of a surface expressed in square feet.
Area per shape: The calculated area of one selected rectangle, circle, triangle, trapezoid, L-shape, or measured area entry.
Net square footage: Repeated area after any deducted area is subtracted.
Waste allowance: Extra square footage added for cuts, errors, pattern matching, breakage, or retained repair material.
Order area: Net square footage plus the entered waste allowance.
Package coverage: The square feet covered by one box, roll, pack, bundle, pallet, or other purchase unit.
Purchased coverage: The total square feet bought after whole-package rounding is applied.
Surplus area: Purchased coverage left after the order area is covered on paper.

References:

Geometric Formulas, OpenStax Prealgebra.
NIST Special Publication 1020, area conversion factors, National Institute of Standards and Technology.
How to Calculate Square Footage, The Home Depot.
How To Measure for Flooring, Build.com.
How to Lay Tile, The Home Depot.