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Grass Seed Calculator: Weight & Packs

Measure your lawn, use the seed rate for your chosen product and purpose, then estimate seed weight and whole packs. No sowing rate is assumed.

1. Measure your lawn

Area actually receiving this product; already exclude anything you are leaving out.

Lawn section

Name or an area to leave out (optional)
Optional measured exclusion within this section. Do not subtract it again from known area.

2. Your product details

Preview only: choosing a product does not fill in any numbers.
Choose specific listed facts, then apply them explicitly. Measurements and extras stay yours.
Manual product facts — no listed source applied.
Enter or check your own product details
Required for seed quantities. This records your decision; it does not choose or recommend a rate.
A range retains both endpoints; no average is calculated.
Your positive rate for the already-chosen purpose. Blank is unknown; there is no recommended value.
Must be at least the lower endpoint. Each known endpoint is calculated separately.
Your actual positive seed mass per pack. Blank leaves whole pack counts unavailable.
No percentage is assumed. Blank means the requirement before extra; it is not a fitting or laying allowance recommendation.

Only your measurements and the facts you choose are used. Confirm suitability and the final order with your supplier.

Enter your lawn measurements to see an estimate.

Private to this browser. Nothing is added to My Materials List automatically.

How the estimate works

Calculator.Shop supplied-fact arithmetic: net lawn area A is the sum of complete nonoverlapping rectangles (length × width) and circles (π × (diameter / 2)²), less each measured exclusion once, or your already-net known area. Extra E = A × your supplied allowancePercent / 100; adjusted area T = A + E. Seed grams g = T × your supplied g/m² rate; kilograms kg = g / 1000. A range keeps its lower and upper rates separately, rejects upper < lower and never averages. For each known endpoint, whole packs = purchaseUnits(required kg, supplied packKg), using the shared safe final ceiling and near-integer floating-point normalisation. Purpose is required for seed computation, but never chooses or multiplies a rate.

Quantity arithmetic only for your already-chosen purpose and entered rate facts. No recommended seed rate, product, species, mix, agronomy, sowing method, fitting allowance or suitability advice. Missing rate or pack mass stays unknown; purpose and pack mass cannot establish a rate. Whole packs do not guarantee sufficient seed, germination, stock or price. No source-derived presets, intermediate rounding or automatic range average.

Reading your result

Grams and kilograms show the seed amount for your supplied rate. Pack counts use the chosen pack mass. A rate range keeps its lower and upper results separate; neither endpoint is a universal recommended rate.

Worked example

Hypothetical arithmetic only, not a recommended sowing rate or pack: a complete 5 m × 4 m lawn section gives 20 m² net area. With manual purpose chosen, a supplied single rate of 30 g/m², no extra allowance and a supplied 0.9 kg pack, seed = 20 × 30 = 600 g = 0.6 kg; ceil(0.6 / 0.9) gives 1 whole pack. These example numbers are not presets or a product suitability claim.

What to measure

Measure the actual lawn area receiving seed. Use complete rectangular or circular sections, deduct measured exclusions once and confirm nonoverlap when combining sections. For another shape, enter a reliable already-net known area rather than a bounding rectangle. Record your already-chosen purpose, then enter your own rate facts as a single rate or two endpoints. Enter a pack mass only if known. All numerical inputs start blank.

How is lawn area measured?

Use complete rectangular or circular sections and deduct each measured exclusion once. More than one complete section requires your explicit nonoverlap confirmation. Known area must already be net; exclusions are not deducted from it again.

Does new lawn or overseeding choose a rate?

No. Purpose records your already-made decision and is required before seed quantities are calculated. Enter your own positive g/m² rate for that purpose; there is no recommended or default rate.

How is a rate range handled?

The lower and upper endpoints each produce their own grams, kilograms and, when pack mass is known, whole pack count. Equal endpoints are allowed; an upper endpoint below the lower is rejected. The calculator never averages a range.

What happens if a rate or pack mass is unknown?

Your measured area and available supplied facts remain visible. A missing rate has no dependent seed mass or pack count. In range mode, a known endpoint can still be calculated while the other stays missing. A known rate without pack mass gives seed mass but no pack count.

Is an extra allowance included automatically?

No. Blank adds no extra and shows before-extra requirements, not a recommended waste or fitting percentage. Your explicit zero gives the same arithmetic but is recorded as supplied. A positive extra is applied to net area once.

Do whole packs guarantee enough seed?

No. Counts are safe whole-number purchase arithmetic for your supplied rate and pack mass. They do not approve a product or sowing method or guarantee germination, sufficient material, stock or price.

Where the numbers come from

Formula v1.0. Numerical product facts start blank unless you explicitly apply a verified option. Supplier facts checked 14 November 2026; they do not establish stock, delivery, suitability or a final order.

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