Crop Seeding Rate, Germination and Seed Cost Calculator

Table of contents

• How to use
• Common mistakes
• Definitions
• Methodology
• Limitations & assumptions
• Sources

Target established plants: The number of crop plants wanted per acre after germination and field losses.

Germination from seed tag: The percent of tested seed expected to germinate under the tag test conditions.

Pure seed from seed tag: The percent of a seed lot that is the named crop seed, rather than inert material or other seed. Pure live seed commonly combines purity and germination. [1]

Expected field establishment of viable seed: The estimated percent of viable seed that becomes established plants after planting and field losses.

Combined usable establishment rate: Germination, purity, and expected field establishment multiplied as decimal fractions.

Exact sales units required: The fractional number of count units or bags needed for the calculated field requirement before ordering is rounded up.

Whole sales units to buy: The exact requirement rounded up to a whole count unit or bag.

Seeds to drop per foot of row: The planter-facing seed rate calculated from adjusted seeds per acre and row spacing.

Mistake: Entering the wanted final stand as if it were the number of seeds planted in Target established plants.
Fix: Enter the desired established plants per acre. The calculator increases the planting rate for the entered losses.

Mistake: Typing 0.95 for Germination from seed tag when the tag says 95%.
Fix: Enter 95 or 95%, because this field uses whole percentages.

Mistake: Treating Pure seed from seed tag and Germination from seed tag as the same percentage.
Fix: Copy each seed-tag value into its own field. Both factors affect the adjusted seeding rate.

Mistake: Using total farm acres instead of Planted field area.
Fix: Enter only acres that will be seeded, excluding intentionally unplanted ground.

Mistake: Filling in count-unit quote values while How is the seed sold? is set to weight-based bags.
Fix: Match the selected sales format to the quote, then enter the visible package fields for that format.

Mistake: Expecting Seed-used cost before package rounding to equal Estimated purchase cost after rounding.
Fix: Use the purchase estimate for ordering. It includes whole-unit rounding and any entered delivery charge or sales tax.

• The calculation depends on the entered target stand and field-establishment estimate. It does not choose a crop population or replace local agronomy advice.
• Seed-tag germination is a test value. Actual emergence can differ with soil temperature, moisture, planting depth, seedbed condition, pests, equipment performance, and other field conditions.
• Purity, germination, seed count per pound, package contents, and price can vary by lot and dealer quote. Use the current documents for the seed being purchased.
• Whole sales units are rounded up because partial bags or count units may not be available. Actual ordering rules, minimums, discounts, freight, and taxes may differ from the entered values.
• Row-spacing outputs describe an even average along rows. They do not verify planter calibration, singulation, skips, doubles, or uneven field placement.
• A zero Planted field area produces no seed order or added charges, even if optional charges contain numbers.

Calculation steps

The calculator first changes the three percentage inputs into decimal fractions and multiplies them. This gives the share of bulk seed expected to become established crop plants under the entered assumptions.

η (combined usable establishment rate) = (germination / 100) * (purity / 100) * (field establishment / 100)

The adjusted planting rate is the target established stand divided by η.

adjusted seeds per acre = target established plants per acre / η

The field seed requirement is the adjusted per-acre rate times planted acres.

adjusted seeds for the field = adjusted seeds per acre * planted field area

For seed sold by count, the field seed requirement is divided by Seeds in each sales unit. For seed sold by weight, it is divided by Seed count to find pounds, then divided by Seed in each bag to find bags. The ordering quantity rounds any positive fractional unit up to the next whole unit.

whole sales units to buy = ceiling(exact sales units required)

The estimated purchase cost uses whole sales units times the applicable quoted price. If there is a seed order, the calculator then adds the optional delivery or order charge and sales tax on the rounded seed purchase. Tax does not apply to the fixed order charge in this calculation.

Worked example

With a target of 34,000 plants per acre, 95% germination, 99% purity, and 90% field establishment, η is 0.84645. The adjusted rate is about 40,168 seeds per acre. For 40 acres, that is about 1,606,710 seeds. If each sales unit contains 140,000 seeds, the exact requirement is about 11.48 units, so the order rounds to 12 units. At $70 per unit with no optional charges, the estimated purchase cost is $840.

Row spacing calculation

If Row spacing (inches) is entered, the calculator converts the per-acre rate into a per-row-foot drop rate using 43,560 square feet per acre and 12 inches per foot.

seeds per row foot = adjusted seeds per acre * row spacing in inches / (43,560 * 12)

average space between dropped seeds in inches = 12 / seeds per row foot