Add up your lawn's shapes, subtract the house and driveway — get the square footage every other lawn number depends on.
The measuring math
rectangle = length × width · circle = diameter² × 0.785
lawn = sum of grass shapes − everything inside that isn't grass
No lawn is a rectangle, but every lawn is a few rectangles and a circle glued together. Measure the big shapes generously, subtract the hardscape honestly, and the answer lands within a few percent — the same accuracy the pros bill for.
A worked example
A 60×40 front yard (2,400 sq ft) plus a 30×25 back (750) minus a 150 sq ft bed and path: 3,000 sq ft — exactly 3.0 of the "per 1,000" units on every fertilizer bag. A bag rated to cover 5,000 sq ft does this lawn 1.7 times; the spreader math on thefertilizer calculatortakes it from there.
Measure once, use everywhere
This number feeds thefertilizer andseed calculators (and every tool we add). The inputs above remember themselves on this device, so the next tool you open here already knows your lawn.
Frequently asked questions
How do I measure my lawn's square footage?
Break the lawn into simple shapes — rectangles (length × width), circles, triangles — measure each with a tape or by pacing (one big step ≈ 3 feet), and add them up. Then subtract the footprint of anything inside that isn't grass: house, driveway, beds, patio. This calculator does the adding and subtracting for you.
Can I get my lawn size from Google Maps instead?
Yes — right-click on Google Maps and use 'Measure distance' to trace your lawn's edges, or use a free area tool. It's accurate to within a few percent, which is plenty. Pacing it off works nearly as well: lawn products aren't dosed so precisely that 5% matters.
Why does lawn square footage matter so much?
Every product doses by area: fertilizer in pounds per 1,000 sq ft, seed in pounds per 1,000, lime, pre-emergent, even watering in inches over the area. Guess your size 40% wrong (most people do) and every application all season is 40% wrong with it — too little does nothing, too much burns grass and wastes money.
What's an average lawn size?
US lawns average around 10,000 sq ft (a quarter acre lot minus the house) but the spread is huge — townhouse lawns run 500–2,000, suburban lots 5,000–15,000, and rural properties measure in acres (43,560 sq ft each). Which is exactly why 'apply one bag' advice fails: bags don't know your lawn.