Spreader Calibration Calculator for Fertilizer, Lime & Seed
Spread pattern width across the ground
Length driven or walked
Weight of material + spreader before run
Weight remaining after test strip
From your seed, lime or fertilizer calculation
Calibration check
4.38 lb / 1,000 sq ft (191 lb/acre)
3.5 lb
4.0 lb
Clemson HGIC 1657 method: 8 ft swath × 100 ft strip = 800 sq ft. 3.5 lb ÷ 800 × 1,000 = 4.38 lb/1,000 sq ft.
Start from your soil-test lab's recommendations and your state extension's planting dates. Always follow product labels.
Spread over a measured strip and weigh what came out. Clemson's method: an 8-ft swath on a 100-ft strip is 800 sq ft; if 3.5 lb went out, the rate is 4.38 lb per 1,000 sq ft (about 191 lb/acre). Adjust the gate and repeat until it matches your target.
How it's calculated
Strip area: Area (sq ft) = swath width (ft) × strip length (ft).
Rate per 1,000 sq ft: Rate = applied pounds ÷ strip area (sq ft) × 1,000.
Rate per acre: Rate (lb/acre) = rate per 1,000 sq ft × 43.56.
Target for strip: Expected pounds = target rate per 1,000 sq ft × strip area (sq ft) ÷ 1,000.
Deviation: Deviation % = (measured rate − target rate) ÷ target rate × 100. Within 10 % of target counts as a pass (the 10 % tolerance is our UI choice).
Sources
- Clemson HGIC 1657 — Calibrating Spreaders
Test-strip method and example
- UGA Extension C798 — Calibration of Dry Broadcast Fertilizer Applicators (2024)
Further reading on spread patterns
Last reviewed: 2026-10-26
Built and maintained by Numberwright. The formulas come from university extension publications (Mississippi State, Clemson, Alabama Extension) and USDA NRCS, linked below. Found a mistake? Contact details coming soon.
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