Square Footage & Room Area Calculator

Intro

Use this square footage and room area calculator to measure a rectangular room, total several rooms, or split an L-shaped floor into simple sections. Enter feet and inches or meters to see measured area in square feet, square meters and square yards, plus an optional material allowance and cost estimate.

What this calculator does

Section 1 is the main rectangle. Sections 2 and 3 let you include a second room, an alcove or another rectangular part of the same floor. Leave both dimensions of an unused optional section at zero. The calculator adds the sections; it cannot detect overlap, so your sketch and measurements determine whether the total is accurate.

Use the same measurement system throughout. In feet mode, enter feet in the main dimension fields and extra inches in the separate fields. In meter mode, use decimal meters: for example, 3 meters 25 centimeters is 3.25 meters. Changing the unit selector reinterprets the entered numbers; it does not convert your measurements automatically.

How it works

For each rectangle, area = length × width. For multiple sections, total measured area = area 1 + area 2 + area 3.

Feet and inches are combined before multiplication: decimal feet = feet + inches / 12. Therefore 12 feet 6 inches is 12.5 feet, not 12.6 feet. Keep full measurements through the calculation and round only the final answer.

The area conversions use the international foot:

• Square meters = square feet × 0.09290304.
• Square feet = square meters / 0.09290304.
• Square yards = square feet / 9.

The material estimate is measured area × (1 + allowance percentage / 100). Cost is that coverage multiplied by your price in the selected area unit. Prices per square meter are applied to square meters, even when you measure the room in feet.

Example calculation

Area = length × width. Material coverage = area × (1 + allowance / 100). Apply the price only after calculating the coverage in the correct price unit.

Try the 120 sq ft example. The US example uses USD; select your region for another currency. It excludes installation, tax and whole-pack rounding. The 10% allowance is an editable illustration, not a material recommendation.

Feet and inches example

Try the feet and inches example. This reproduces the measurement and allowance steps in the planned DIY room-measurement guide. If a chosen carton covers 20 sq ft, 140.9375 ÷ 20 = 7.046875, so an order would need 8 cartons. Carton coverage and rounding are manual here; this calculator does not calculate pack counts.

L-shaped room example

Split the floor into a 12 × 10 ft rectangle and a separate 6 × 4 ft rectangle: 120 + 24 = 144 sq ft. The rectangles must not overlap at the corner. Use a sketch to identify the boundaries. The result diagram explains rectangle multiplication; it is not a floor plan drawn from your measurements.

Try the two-section example. This example uses zero allowance so you can check the measured area directly.

Metric price example

A 4 × 3 m room is 12 sq m. With a 10% example allowance: 12 × 1.10 = 13.2 sq m. At $20 per square meter: 13.2 × $20 = $264. The selected price unit determines the cost calculation even when dimensions use another unit system.

Try the metric example. Switching measurement units reinterprets the inputs; it does not convert numbers already entered. These links restore the complete example inputs and recalculate using the current calculator.

How to use the result

Use measured area to compare room sizes. Use coverage including allowance as a starting point for material ordering, then check pack coverage and round up to whole packs with your supplier. The example 10% allowance is editable; appropriate waste depends on material, layout, cutting and installer practice.

Measure at floor level for flooring. A room's floor area is not its wall area: use the Paint Calculator for wall painting. If you already know an area and only need another unit, use the Unit Converter.

Assumptions and limitations

• All sections are rectangles with straight sides and right angles. Approximate curved areas separately rather than treating them as exact rectangles.
• Add only non-overlapping sections. The calculator does not subtract openings or check the geometry of an L-shape.
• Optional sections are omitted only when both complete dimensions are zero. A missing width or length produces an error.
• Waste allowance affects material coverage, not measured room size. It can be set from 0% to 100%.
• A zero material price skips the cost estimate. Costs exclude labor, tax, delivery, adhesives, underlay, trims and whole-pack rounding.
• The calculator displays rounded figures but uses unrounded area for totals and cost. Very small nonzero areas use scientific notation to avoid appearing as zero.
• This is a planning tool, not a certified property measurement or a check against local floor-area reporting rules. Check important measurements with your installer or surveyor.

Sources and calculation review

The exact international-foot area conversion is listed in NIST unit conversion factors. Conversion basis checked on 15 October 2026. The room and material calculations are shown above so you can check them against your measurements and supplier's specifications.

How we explain formulas, assumptions and sources