Square Footage Calculator: How to Calculate Square Footage

How to Enter Feet and Inches

Decimal feet = whole feet + inches ÷ 12. A measurement of 12 ft 6 in is 12.5 ft, not 12.6 ft. Likewise, 10 ft 3 in is 10.25 ft. Convert each dimension before multiplying.

For that room: 12.5 × 10.25 = 128.125 sq ft. Two rooms with those exact dimensions total 256.25 sq ft. Enter 2 in Number of identical sections only when both rooms have the same length and width.

The same room measures 3.81 m × 3.1242 m and has 11.903202 m² of area. The calculator displays 11.903202 m². Switching units converts the current dimensions rather than loading another room.

Calculate square footage from your room measurements

Add Different-Size Rooms Separately

A 12 × 10 ft room has 120 sq ft; an 8 × 6 ft room has 48 sq ft. Together they have 168 sq ft. Do not enter 2 as the section count for the first room: that would calculate two 120 sq ft rooms and give 240 sq ft.

Use count 1 for each different rectangle and add its result to your takeoff. Keep enough precision until all areas have been combined. Include closets or alcoves if they receive the material, but do not count an area twice.

Measure an L-Shaped Room Without Double Counting

Split an L-shaped layout into two rectangles that share an edge but do not overlap. For example, a 12 × 10 ft main area plus a 6 × 4 ft extension totals 120 + 24 = 144 sq ft. Measure the extension outside the main rectangle.

As an alternative for the same layout, a surrounding 18 × 10 ft rectangle minus a missing 6 × 6 ft corner gives 180 − 36 = 144 sq ft. Use one method; do not add the full surrounding rectangle to the extension.

Draw the sections and write each dimension next to its edge before entering numbers. Slanted walls, curves and triangles need an appropriate area formula or a more detailed takeoff. The calculator itself multiplies rectangles; it does not automatically model an irregular outline.

Measured Area Is Not the Final Material Order

For a measured 144 sq ft floor, a selected 10% material waste allowance produces 158.4 sq ft to cover. If the chosen carton covers 20 sq ft, 158.4 ÷ 20 = 7.92, so purchase 8 cartons covering 160 sq ft. The allowance and carton size are hypothetical; use the supplier’s guidance for your layout and product.

The square-footage tool reports area only. Add material waste and round packaging separately, and do not add waste twice. For mulch, gravel or concrete, area also needs a depth to establish volume. For paint or drywall, measure the wall and ceiling faces instead of assuming floor area is the finishing area.

Estimate flooring material and whole packages

Estimate paint from the surfaces being painted

What Is Square Footage?

Square footage is the measurement of an area's size expressed in square feet.

It is commonly used for:

• Flooring
• Paint
• Roofing
• Concrete
• Landscaping
• Decks
• Patios
• Real estate

How to Calculate Square Footage

Basic Formula:

Length × Width = Square Footage

For example:

20 ft × 15 ft = 300 square feet

For irregular areas, divide the space into smaller rectangles, calculate each section separately, and add the totals together.

Example Calculation

Living Room

Length: 18 feet

Width: 14 feet

Result:

18 × 14 = 252 square feet

Where Square Footage Is Used

Square footage is commonly used when estimating:

• Flooring
• Carpet
• Tile
• Paint
• Concrete
• Drywall
• Roofing
• Sod
• Mulch
• Gravel

Review the Layout Before Ordering Materials

Square footage tells you how much area a room contains. Before finalizing a new room or remodel layout, also check furniture placement, door swings, and the routes people will use through the space. Two rooms with the same area can function very differently.

The Big Floor Plans Floor Plan Review Checklist can help you organize layout questions to discuss with your designer or builder. It is an external planning resource from a company that sells full-scale printed floor plans; it does not replace professional design or code review. Once the layout is settled, use its confirmed dimensions for your material estimate.

Explore the Big Floor Plans Floor Plan Review Checklist

Common Mistakes

Check these points before finalizing your measurements:

• Measuring only one wall
• Forgetting closets or alcoves
• Mixing feet and inches
• Forgetting to subtract openings when necessary
• Rounding measurements too early