Direct Sow Rate Calculator

Use bed mode for rectangular plots, or row mode for measured rows. Spacing controls the sowing rate, while germination and survival adjust real-world losses.

These examples show common spacings and typical germination ranges. Always check your seed packet and local conditions.

1. Choose a unit system, then pick bed mode or row mode.
2. Enter bed size or row length, plus beds and successions.
3. Set row spacing and seed spacing from your crop guide.
4. Enter germination, survival, and thinning values for your site.
5. Add an oversow buffer if you expect uneven emergence.
6. Calculate, then download CSV or PDF for field notes.

Purpose of a sow rate plan

Direct sowing succeeds when seed supply matches the space you are planting. This calculator turns your bed or row layout into a repeatable sowing rate, so you can budget seed, avoid thin stands, and document results across seasons. It is useful when small spacing changes create large differences in seed demand for every crop cycle.

Translating bed geometry into row length

In bed mode, planted row length is estimated from bed length and the number of rows that fit across the bed width using your row spacing. If you plant bands, choose a tighter row spacing to represent the band width. In row mode, you enter row count and row length directly, which suits tunnels and market blocks. Successions multiply planted length for multiple sowing dates, supporting weekly or biweekly plans.

Spacing, density, and target populations

The base seed requirement is driven by in-row spacing. Divide total planted row length by seed spacing to estimate how many seed placements you intend. The tool also reports seeds per area and seeds per row length, which helps you confirm that the plan aligns with crop recommendations. If a crop is thinned, treat seed spacing as drop spacing.

Adjusting for field losses and management

Real gardens lose plants to uneven germination, pests, damping-off, crusted soil, and thinning decisions. The calculator applies germination, survival, thinning keep-rate, and edge loss to estimate an expected success fraction, then scales up your seed count. An oversow buffer adds insurance for gaps, washouts, and re-sowing after birds or heavy rain.

Using outputs for purchasing and scheduling

Round up required seeds, then translate them into packets or weight using the optional fields for seeds per gram or seeds per ounce. This supports bulk buying and helps prevent shortages. Keep records by downloading CSV for spreadsheets or PDF for field notes. Use the results to stage seed orders, allocate bed space per succession, and coordinate irrigation, weeding, and thinning windows with realistic labor targets.

What oversow buffer should I use?

Start with 5–10% for fresh seed in good soil. Use 10–20% for cold soils, older seed, or pest pressure. Increase further if you expect washouts, bird damage, or uneven irrigation.

How do I set the thinning keep-rate?

If you thin to final spacing, enter the percent of seedlings you plan to keep. For example, keeping one plant out of two is 50%. If you do not thin, leave it at 100%.

Can this calculator handle broadcast sowing?

Yes. Treat seed spacing as a proxy for target density. Use a smaller spacing value to represent a heavier broadcast rate, then validate the seeds-per-area output against your crop guideline or past results.

Why does row spacing matter in bed mode?

Bed mode estimates how many rows fit across the bed width. Wider row spacing reduces rows per bed, shortening total planted row length. That lowers the base seed count and changes seeds-per-area calculations.

How can I estimate packets or weight?

Enter seeds per gram or seeds per ounce to estimate weight needed. If packets list a seed count or a weight, fill those fields too. The results show approximate packet quantities, which you should round up.

Which inputs change the result the most?

Seed spacing, successions, and germination are usually the biggest drivers. Survival, thinning, and edge loss refine the estimate for your site. Row spacing mainly affects bed mode because it changes the estimated number of rows.