Lawn Area Calculator
Measure rectangles, circles, and triangles. Convert area units.
For a rectangular lawn, multiply length by width. A 20 × 10 ft lawn covers 200 square feet, equivalent to about 18.58 square meters, 22.22 square yards, or 0.00459 acres.
How to use this calculator
- Sketch the lawn outline and mark surfaces you do not want included. Separate irregular ground into simple shapes that do not overlap.
- Select rectangle, circle, or triangle. Measure a circle through its center to get diameter; for a triangle, measure height at a right angle to the base.
- Choose feet or meters before entering dimensions. Keep all horizontal measurements for a calculation in that same unit.
- Calculate each section and add the areas. Subtract patios, planting beds, and other excluded spaces. Carry the final area to the material calculator for your project.
Understanding the formula
A rectangle contains length times width square units. A triangle occupies half of a rectangle with the same base and perpendicular height. A circle’s area is π times radius squared; radius is half the diameter. Conversion applies to area, so the length factor must be squared. One square foot equals 0.09290304 square meters, and 43,560 square feet equals one acre using international-foot units.
Worked examples
A circular lawn
For a 16 ft diameter circle, the radius is 8 ft. Its area is π × 8², approximately 201.06 sq ft. Enter 16 in the Diameter field; using 8 there would calculate only one quarter of the intended area.
An L-shaped lawn
Split an L shape into a 20 × 10 ft rectangle and an adjoining 8 × 6 ft rectangle with no overlap. Their areas are 200 and 48 sq ft, totaling 248 sq ft. Subtract a 4 × 4 ft bed to leave 232 sq ft.
A triangular corner
A corner with a 12 ft base and 8 ft perpendicular height has an area of 12 × 8 ÷ 2 = 48 sq ft. The sloping edge is not the height unless it happens to be perpendicular to the chosen base.
Lawn area conversion reference
| Square feet | Square meters | Acres |
|---|---|---|
| 100 | 9.2903 | 0.002296 |
| 500 | 46.4515 | 0.011478 |
| 1,000 | 92.9030 | 0.022957 |
| 43,560 | 4,046.8564 | 1 |
Using area to plan materials
Area alone does not specify a mulch depth, seed rate, or soil thickness. After measuring, use the related material calculator and its product-specific inputs. This tool uses international-foot conversion factors documented by NIST. It estimates simple surface footprints; it is not a cadastral survey or a property-boundary determination.
Common measurement and ordering mistakes
- Using a circle’s radius in the diameter field, which reduces the calculated area to one quarter.
- Measuring a triangle along its sloped side rather than taking the perpendicular distance from base to opposite corner.
- Counting overlapping rectangles twice when breaking up an irregular lawn.
- Using total lot acreage as lawn area without subtracting hard surfaces and buildings. For slopes, be clear whether your project needs horizontal plan area or actual surface area.
Frequently asked questions
Can I measure an irregular lawn?
Yes. Divide it into smaller simple shapes, calculate each, and total the non-overlapping areas. Curved boundaries remain approximations.
Why is width hidden for a circle?
A circle is defined by its diameter, so width adds no independent information and is not required.
Does the calculator subtract obstacles?
Not automatically. Calculate the obstacle separately and subtract its area from the total.
Can it measure from a map?
This version accepts dimensions you supply. It does not trace a map or determine boundaries.
Should I add waste to lawn area?
Keep the measured area unchanged. Apply any cutting or handling allowance in the relevant material calculator so the reason for the extra quantity stays clear.
Sources and calculation notes
The tables and examples are calculated from the formulas shown here. These references support the stated unit conversions and the specifically identified planting or installation guidance.
See an error or an assumption that needs clarification? Email contact@yardcalclab.com with the inputs and units you used.