Area formulas for lawn shapes
| Shape | What to measure | Formula | Example |
|---|---|---|---|
| Rectangle | length, width | L × W | 60 × 40 = 2,400 sq ft |
| Circle | diameter | 3.1416 × (D ÷ 2)² | 20 ft across = 314 sq ft |
| Half circle | diameter | 3.1416 × (D ÷ 2)² ÷ 2 | 20 ft across = 157 sq ft |
| Triangle | base, height | B × H ÷ 2 | 30 × 16 ÷ 2 = 240 sq ft |
| Trapezoid | two parallel sides, distance between | (A + B) ÷ 2 × H | (40 + 30) ÷ 2 × 20 = 700 sq ft |
A trapezoid is a rectangle plus a triangle, so you can enter it in the calculator that way.
Converting the result
| To get | From square feet |
|---|---|
| Square yards | ÷ 9 |
| Acres | ÷ 43,560 |
| Square meters | × 0.0929 |
| Thousands of sq ft (for seed and fertilizer rates) | ÷ 1,000 |
The calculator shows all of these at once. For a two-way converter between square feet and acres, see square feet to acres.
A worked example: front and back yard
| Section | Measure | Square feet |
|---|---|---|
| Back lawn | 60 × 40 ft | 2,400 |
| Front lawn | 50 × 22 ft | 1,100 |
| Side yard | 35 × 8 ft | 280 |
| Curved corner bed (cut-out, quarter circle of 10 ft radius) | 3.1416 × 10² ÷ 4 | − 78.5 |
| Patio (cut-out) | 16 × 14 ft | − 224 |
| Tree ring (cut-out) | 6 ft across | − 28.3 |
| Lawn | 3,449.2 sq ft |
That is 383.2 square yards, 0.079 acres, or 3.45 thousand square feet. The calculator has no quarter-circle shape, so work its area out as above (78.5 sq ft) and enter it as a 78.5 × 1 ft rectangle marked as a cut-out.
What to use your lawn size for
| Project | Rate or unit | Where to calculate |
|---|---|---|
| Sod | square feet, plus 5–10% | Sod calculator |
| Grass seed | lb per 1,000 sq ft | Grass seed calculator |
| Overseeding | about half the seed rate | Overseeding calculator |
| Fertilizer | lb of nutrient per 1,000 sq ft | Lawn fertilizer calculator |
| Watering | inches of water | Watering new sod |
| Artificial turf | square feet, by roll width | Artificial turf calculator |
Tips for accurate measuring
- Measure the grass, not the lot. Leave out the house footprint, driveway, walks, beds and patios.
- Use one straight reference line. For long, irregular yards, measure everything from a baseline such as a fence or the edge of the drive.
- Round up a little for sod and turf, where running short is a problem. For fertilizer, round to the nearest number, since over-applying is the bigger risk.
- Write each section down with a sketch. If the numbers look odd later, you can check which one is off.
- Keep the number. Your lawn size doesn’t change, and you’ll use it every season for seed and fertilizer.
Results depend on your measurements. For sod and turf orders, measure twice and confirm piece and roll sizes with your supplier.
Questions people ask
- How do I calculate the square footage of my lawn?
- Split the lawn into rectangles, circles and triangles, measure each in feet and work out its area: length × width for rectangles, 3.1416 × radius² for circles and base × height ÷ 2 for triangles. Add them and subtract beds, patios and other areas that aren't grass.
- How big is the average lawn?
- There isn't a reliable single number, because lot sizes vary so much by region and age of neighborhood. Measuring your own takes about twenty minutes and is the only figure worth ordering with.
- How many square feet are in an acre?
- 43,560 square feet. A quarter acre is 10,890 sq ft and a half acre is 21,780 sq ft. Remember that the lawn is usually much smaller than the lot.
- What do I do with 'per 1,000 sq ft' rates?
- Divide your square footage by 1,000 and multiply by the rate. The calculator's last line shows your lawn in thousands of square feet so you can multiply directly.
- Can I measure my lawn from a satellite map?
- Online map tools give a quick estimate for large areas. Check one or two sides with a tape, because trees, shadows and the image angle can throw the outline off.