How big is my lawn?
Every other number — seed, fertilizer, mulch, irrigation run time — starts here. Break the yard into simple shapes, add the grass, subtract the rest.
- Grass shapes — break the yard into rectangles, triangles, and circles; add each area
- House & hardscape — subtract footprint, driveway, patio, and beds from the total
- Curves — approximate with a rectangle or triangle; close enough for seed and fertilizer rates
How to measure without a survey
Pace it. A normal adult stride is close to 3 feet, so counting steps along each edge gets you within a few percent — plenty for rates published as ranges. Walk each side, write the numbers on your phone, and decompose the shape:
- Rectangles for the front strip, the side yard, the back.
- Circles for a round bed or an island — measure across and halve it.
- Triangles for the wedge where a fence cuts a corner.
Then subtract what is not grass: the house footprint, the driveway, the patio, the beds. Fertilizer applied to a driveway does nothing but run into the storm drain.
The formulas
rectangle = length × width
circle = 3.1416 × radius²
triangle = base × height ÷ 2
acres = square feet ÷ 43,560
Questions people actually ask
How do I measure an odd-shaped lawn?
Break it into rectangles, circles and triangles, measure each one, and add them up. A yard that looks impossible is almost always three rectangles and a curve.
Do I subtract the house, the driveway and the beds?
Yes. Seed, fertilizer and irrigation only apply to the grass. Measure the whole lot, then subtract everything you are not treating — that is what the minus rows here are for.
How accurate does this need to be?
Within about 10%. Seeding and fertilizer rates are published as ranges, so a few hundred square feet either way does not change what you buy — but guessing 'about half an acre' when it is 6,000 sq ft does.
How many square feet are in an acre?
43,560. Most suburban lots are a fraction of that, and the lawn itself is a fraction of the lot.