How to measure your lawn (and why every other decision needs it)

Almost every recommendation on this site — and on every fertilizer bag, spreader setting chart and mower spec sheet — is expressed per unit area. And almost nobody knows their own area. This is the twenty-minute job that makes every other decision possible.

Why the number matters more than you would think

Method 1: split it into shapes

This is the reliable one, and it is the only method that lets you subtract the parts that are not grass.

1. Sketch the lawn roughly on paper. It does not need to be to scale.
2. Draw lines dividing it into rectangles, triangles and part-circles. Overlap nothing.
3. Measure each shape. A long tape is ideal; pacing works if you know your stride.
4. Calculate each area and add them up.
5. Subtract beds, paths, the patio and anything else that is not grass.

Method 2: pace it out

If a long tape is not to hand, your own stride is a usable measuring tool once you have calibrated it.

1. Mark a known distance — a 30 ft driveway, a 20 ft fence run.
2. Walk it normally and count paces.
3. Divide the distance by the paces to get feet per pace.
4. Now pace every side of every shape and multiply.

Method 3: measure it from above

Satellite mapping tools with an area function will let you click round a lawn boundary and read off the area. It is fast and it is good at irregular shapes.

Two cautions. Imagery can be years out of date, so a bed you added last spring may still be lawn on the map. And it is easy to trace the property boundary rather than the grass boundary, which is exactly the over-measurement that shape-splitting avoids. Use it to cross-check a measured figure rather than to replace one.

The conversions to write on the sketch

Keep the sketch. The number changes only when you change the garden, and you will use it every spring for the rest of the time you live there.

What to do with the number

Fertilizer and seed

Divide your area by 1,000 and you have the multiplier for every published rate. A 4,021 sq ft lawn is 4.0 units, so a 1 lb-per-1,000 application is 4 lbs of nitrogen-equivalent, not a bag. Working out how much product that is takes one more step, covered in fertilizer numbers explained.

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Mower sizing

Convert to acres and compare against published ratings. Below 14,520 sq ft you are inside the Greenworks 40V push mower's published third of an acre. Above 21,780 you are past the 80V flagship's half-acre rating and into multiple-pack territory.

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Time and passes

Area divided by working width gives linear feet, and linear feet divided by your run length gives passes. That is how a spreader's 6 ft spread width becomes 14 passes on a 5,000 sq ft lawn, and it is the same arithmetic behind how long it takes to mow an acre.

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What we cannot tell you

We cannot tell you your lawn area, and any site that offers you a "typical" figure is inventing one. Lot sizes vary enormously and the grass fraction of a lot varies more.

What we can tell you is that the measurement takes about twenty minutes, that 43,560 square feet is an acre, and that every published rate in lawn care assumes you have done it.