Spreader calculator

Two jobs in one place: how much product to put down to hit a nitrogen rate, and whether your spreader is actually throwing that much.

The bag and the lawn

Target nitrogen (lb N / 1,000 ft²)

A typical single feed is 0.5 to 1.0.

Nitrogen in the product (%)

The first of the three numbers on the bag.

Area to cover (ft²)

Catch test (optional)

Weight loaded into the hopper (lb)

Weight left afterwards (lb)

Area covered in the test (ft²)

Spread this much

Product rate3.13 lb / 1,000 ft²

Total for 5,000 ft²15.6 lb

What your spreader is doing

Measured rate3.00 lb / 1,000 ft²

Against your targetOn target (-4%)

Within ±10% of the product rate.

How the catch test works

Weigh what goes into the hopper, spread over a measured area at your normal walking pace, then weigh what is left. The difference is what the spreader put down, and dividing it by the area gives the rate it is really running — which is often not the rate on the setting chart.

Anything within ten percent of your target counts as on target here. Beyond that, close the setting down if it is running heavy and open it up if it is running light, then run the test again.