Seed Spacing Calculator
Calculate seeding rates, thinning distances and how much seed a row needs.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
Estimate seed quantity from row length, final plant spacing, sowing density and germination rate. The model allows for the entered germination rate, but actual emergence varies by seed lot and conditions; follow the seed packet for species-specific spacing and thinning timing.
Worked example
calculated with the default values below
Row length 20 ft · Final plant spacing 4 in · Seed spacing when sowing 1 in · Germination rate 80 % · Number of rows 1 Plants required 60 · Seeds to sow 300 · Seedlings to remove when thinning 180 · Seeds to sow per foot 15.00 pcs
General background references
Disclaimer
These are general gardening estimates. Planting windows, growth, water and nutrient needs vary by place and plant. Check local extension guidance and product labels before acting on an estimate.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
F = ⌊12L÷d_f⌋×r; S = ⌈⌊12L÷d_s⌋×r÷(g÷100)⌉; X = max(0, ⌊12L÷d_s⌋×r − F)
- L
- Row length (ft)
- d_f
- Final spacing (in)
- d_s
- Sowing spacing (in)
- r
- Number of rows
- g
- Germination rate (%)
- F
- Final number of plants
- S
- Seeds sown to offset germination losses
- X
- Seedlings removed by thinning
Final plants = floor(row length×12÷final spacing)×rows. Target seed count is the larger of sow-spacing positions and final plant count, adjusted upward by germination percentage; expected thinning uses the estimated germinated count. Actual emergence varies.
Frequently asked questions
Why does the seed count exceed the final plant count?
The target seed count is the greater of the sow-spacing positions and the final plant count, adjusted upward for the entered germination rate. Expected seedlings are estimated from that seed count; thinning is the expected excess above the final plant count. Actual germination and emergence can differ.