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How to Calculate Area
Area measures the two-dimensional space inside a boundary. The formula depends on the shape:
Rectangle or Square
Area = Length × Width
A room that is 15 feet by 12 feet:
The right pane shows 180 ft² (Notes Calculator builds the compound unit automatically).
Triangle
Area = (Base × Height) / 2
A triangle with a 10 m base and 6 m height:
| Note | Result |
|---|---|
| base = 10 m | 10 m |
| height = 6 m | 6 m |
| (base × height) / 2 | 30 m² |
The right pane shows 30 m².
Circle
Area = π × r²
A circular garden with a 5 m radius:
The right pane shows 78.54 m² using the built-in pi constant.
Common Area Unit Conversions
| From | To | Formula |
|---|---|---|
| Square feet | Square meters | × 0.0929 |
| Square meters | Square feet | × 10.764 |
| Acres | Square feet | × 43,560 |
| Square feet | Acres | ÷ 43,560 |
| Hectares | Acres | × 2.471 |
| Acres | Hectares | × 0.4047 |
| Square kilometers | Square miles | × 0.3861 |
| Square miles | Square kilometers | × 2.59 |
Quick Reference
| Unit | Equivalent |
|---|---|
| 1 acre | 43,560 sq ft |
| 1 hectare | 10,000 m² |
| 1 hectare | 2.471 acres |
| 1 sq mile | 640 acres |
| 1 sq km | 100 hectares |
Practical Area Calculations
Room Square Footage (Flooring)
Calculating flooring for a home:
| Note | Result |
|---|---|
| Living room: 15 ft × 18 ft | 270 ft² |
| Bedroom 1: 12 ft × 14 ft | 168 ft² |
| Bedroom 2: 11 ft × 12 ft | 132 ft² |
| Kitchen: 10 ft × 12 ft | 120 ft² |
| total | 690 ft² |
The right pane shows 270 ft², 168 ft², 132 ft², 120 ft², and the total keyword resolves to 690 ft² (it sums every consecutive line above it). Multiply by your cost per square foot to get the flooring bill: for example, 690 × $4.50 is $3,105.
Lot Size for Real Estate
Understanding property sizes when house hunting:
| Note | Result |
|---|---|
| lot = 0.25 acres | 0.25 ac |
| lot in sq ft | 10,890 ft² |
| lot in square meters | 1,011.71 m² |
The right pane shows 10,890 ft² and 1,011.71 m²: Notes Calculator handles the unit conversion natively, so you do not memorize the multipliers.
For calculating mortgage payments on a property, see our loan payment calculator.
Agricultural Land
Converting between hectares and acres for farmland:
| Note | Result |
|---|---|
| farm = 120 hectares | 120 ha |
| farm in acres | 296.53 ac |
| farm in sq km | 1.20 km² |
The right pane shows 296.53 ac and 1.20 km².
Free Area Calculator
Convert between square feet, square meters, acres, hectares, and more.
©2026 Notes Calculator. All rights reserved.
Example
Convert 2,500 sq ft to square meters:
| Note | Result |
|---|---|
| 2500 sq ft in square meters | 232.26 m² |
Frequently Asked Questions
How do I calculate the area of a room in square feet?
Measure the length and width of the room in feet, then multiply them together. For example, a room that is 15 feet by 12 feet has an area of 15 x 12 = 180 square feet. For irregular rooms, divide them into rectangles, calculate each area separately, and add them together.
How many square feet are in an acre?
One acre equals exactly 43,560 square feet. To convert acres to square feet, multiply by 43,560. To convert square feet to acres, divide by 43,560. For reference, an acre is roughly the size of a football field (about 48,000 sq ft without the end zones).
What is the difference between hectares and acres?
A hectare is a metric unit equal to 10,000 square meters (100m x 100m). An acre is an imperial unit equal to 43,560 square feet. One hectare equals approximately 2.471 acres. Hectares are used in most of the world, while acres are common in the US, UK, and Canada.
Calculate Area in Notes Calculator
Notes Calculator supports area units and compound unit arithmetic:
| Note | Result |
|---|---|
| // Split an L-shaped room into two rectangles | |
| main part = 14 ft x 10 ft | 140 ft² |
| alcove = 6 ft x 4 ft | 24 ft² |
| room = main part + alcove | 164 ft² |
| room in square meters | 15.24 m² |
| // Round patio | |
| patio radius = 2 m | 2 m |
| patio = pi * patio radius * patio radius | 12.57 m² |
| patio in sq ft | 135.26 ft² |
| // Side of a square room of 400 sq ft, in feet | |
| sqrt(400) | 20 |
| // Land conversion | |
| field = 3 hectares | 3 ha |
| field in acres | 7.41 ac |
When you multiply two length values like 14 ft x 10 ft, Notes Calculator automatically creates a compound unit (ft²). The pi constant is built in, and sqrt() lets you calculate side lengths from areas. Use headings (#) to separate different rooms or properties, and total to sum areas across rooms.
For a site visit that turns a room measurement into a materials order and a job quote, the calculator for contractors and tradespeople divides a floor area by the size of one tile, adds a cut allowance, works out paint for two coats and prices labor and marked-up parts on the same note.
When the area you measured is a lawn, a garden bed or a field, the calculator for landscapers and farmers turns it into mulch in cubic yards, seed by the acre and a cost per acre on the same page.
For other unit conversions, see our unit converter. For calculating material costs based on area, variables and totals in a notepad calculator make the math easy.