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Soybean Yield Estimate Calculator — Plants, Pods, Seeds & Seed Weight

Estimate soybean yield before harvest from plants per m², pods per plant, seeds per pod and 1,000-seed weight — in t/ha, kg/ha and bushels per acre, with a seed-size sensitivity table.

Plants per square metre

Pods per plant

Seeds per pod

Weight of 1,000 seeds

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How it works

Seeds per m² = plants/m² × pods per plant × seeds per pod · Yield (kg/ha) = seeds per m² × 1,000-seed weight (g) ÷ 1,000 × 10 · bu/acre = kg/ha × 0.8922 ÷ 60

Soybean yield is the product of four components: plants per area, pods per plant, seeds per pod and seed size. Extension services (Iowa State, Purdue, INTA) use exactly this component method from about the R6 stage, when pods are full of green seeds. The first three can be counted; seed size is only known at maturity, so use a typical 1,000-seed weight and treat the result as a range — late-season drought that shrinks seeds can cut yield by 20% or more.

Worked example

30 plants/m² × 40 pods × 2.5 seeds per pod = 3,000 seeds/m². At 150 g per 1,000 seeds that is 450 g/m², or 4,500 kg/ha = 4.50 t/ha (66.9 bu/acre). With smaller 120 g seeds the same field would yield 3.60 t/ha.

Sources: Iowa State University Extension — Soybean yield estimates · Purdue University — Estimating soybean yields

Frequently asked questions

When is the best time to estimate soybean yield?

From growth stage R6 (full seed), when pod numbers are set. Earlier counts overestimate because plants still abort flowers and young pods; the seed-size assumption is the main remaining uncertainty.

How do I count plants per square metre?

Count the plants in 1 m of row in several places and divide by the row spacing in metres — for example 15 plants in 1 m at 0.52 m rows = 28.8 plants/m². Alternatively count inside a 1 m² frame.

What is a normal 1,000-seed weight for soybean?

Most varieties weigh 120–200 g per 1,000 seeds; 150–160 g is a common average. US agronomists express the same thing as seeds per pound, around 2,500–3,000.

How accurate are pod-count yield estimates?

They typically land within 10–20% of the harvested yield. Sample at least 5–10 spots, avoid field edges, and remember that harvest losses (often 2–5%) and seed moisture are not included.

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This calculator is for educational purposes. Double-check important results before acting on them.