Seeds per Foot of Row Calculator

This calculator works out how many seeds you need per foot of row, based on your row length, spacing between seeds, and the expected germination rate. You enter the row length, the spacing you plan between seeds, and the germination percentage, and it returns the total seeds needed, plus the seeds per foot and the number of seeds to sow per hole for hill planting. The first output, total seeds, is the headline answer.

Formula

The core formula is straightforward: divide the row length (converted to inches) by the seed spacing to get the number of planting spots, then adjust for germination.

Total seeds = (Row length in feet × 12) ÷ Seed spacing in inches × (100 ÷ Germination rate %)

Where:

• Row length (l) – the length of the row you are planting, in feet.
• Seed spacing (s) – the distance between individual seeds in the row, in inches.
• Germination rate (g) – the percentage of seeds expected to sprout (e.g., 85 means 85%).

The result is rounded up to the nearest whole seed because you cannot plant a fraction of a seed. The seeds-per-foot output uses the same logic but for a 1-foot section, and the per-hole output tells you how many seeds to drop in each hole if you are planting in hills (for example, beans or squash) rather than a continuous row.

Worked Example

Using the default values from the calculator: row length = 20 ft, seed spacing = 4 inches, germination rate = 85%.

1. Convert row length to inches: 20 ft × 12 = 240 inches.
2. Divide by seed spacing: 240 ÷ 4 = 60 planting spots.
3. Adjust for germination: 60 × (100 ÷ 85) = 60 × 1.17647 = 70.588 seeds.
4. Round up: 71 seeds total.

Seeds per foot: (12 ÷ 4) × (100 ÷ 85) = 3 × 1.17647 = 3.53 seeds/ft. Seeds per hole: 100 ÷ 85 = 1.18, rounded up to 2 seeds per hole.

Why Germination Rate Matters

Seed packets often list a germination percentage, but that is a lab measurement under ideal conditions. In real garden soil, germination can be lower due to temperature, moisture, soil contact, and seed age. If you sow exactly one seed per spot and the germination rate is 85%, you will end up with gaps. The calculator builds in a buffer by dividing by the germination rate. For example, with 85% germination, you plant about 18% extra seeds (100/85 ≈ 1.18). If you have old seeds or poor conditions, you might want to use a lower germination percentage than the packet states.

How to Choose Seed Spacing

Spacing depends on the crop and the final plant size. Check the seed packet or a planting guide for the recommended spacing for your specific variety. Here are some common examples:

• Carrots: 1–2 inches apart
• Lettuce: 4–6 inches apart (for full heads)
• Beans: 3–4 inches apart
• Corn: 9–12 inches apart
• Squash (hills): 24–36 inches between hills, 2–3 seeds per hill

If you are thinning later, you can sow more densely and thin to the final spacing. The calculator can help you estimate how many seeds to buy or start with.

Common Mistakes

• Mixing units: Row length is in feet, but seed spacing is in inches. Always convert one to the other. The calculator does this automatically, but if you are doing it by hand, remember 1 ft = 12 in.
• Forgetting germination: If you skip the germination adjustment, you will under-plant. Always include it, even if it is 100% (then the factor is 1).
• Rounding too early: Do not round intermediate results. Only round the final answer up to the next whole seed.
• Using the wrong spacing for hills: For hill planting, the spacing between hills is large, but the seeds per hill is a separate number. The calculator gives you both.

Limitations of the Formula

This calculator assumes uniform spacing and a single germination rate. It does not account for:

• Seed size or planting depth: Larger seeds may need deeper planting, but that does not affect the count.
• Soil conditions: Crusting, pests, or poor moisture can reduce actual emergence beyond the germination rate.
• Thinning: If you plan to sow thickly and thin later, you will need more seeds than the calculator suggests. You can adjust by entering a wider spacing (the final spacing) and then multiply by a factor for overseeding.
• Row length in meters: If you work in metric, convert feet to meters (1 ft = 0.3048 m) and inches to cm (1 in = 2.54 cm) before using the formula.

For very small seeds (like lettuce or carrots), it is often impractical to space them individually. In that case, you might sow by weight or use a seed tape. This calculator is best for seeds that are large enough to place individually.

Practical Tips for Using the Result

• Buy a little extra seed than the calculator says, because counting seeds in a packet is tedious and you might drop one.
• If you are planting multiple rows, multiply the total by the number of rows.
• For direct-seeded crops, you can use the seeds-per-foot number to calibrate a hand seeder or to check your sowing rate.
• If the germination rate is unknown, use a conservative estimate (e.g., 70%) to avoid gaps.

Frequently Asked Questions

How many seeds do I plant per hole?

For crops that are typically planted in hills (squash, cucumbers, melons), plant 2–3 seeds per hill and thin to the strongest seedling. The calculator’s per-hole output gives you the minimum number to ensure at least one germinates, based on the germination rate. For example, with 85% germination, it suggests 2 seeds per hole.

What if my seed packet doesn’t list germination rate?

Most packets do list it, but if not, assume 80–90% for fresh seeds. Older seeds may be lower. You can do a simple germination test: place 10 seeds on a damp paper towel, keep them warm, and count how many sprout after the expected time. Use that percentage in the calculator.

Can I use this calculator for flower seeds?

Yes, as long as you know the recommended spacing and germination rate. Many flowers are direct-sown, and the same math applies. For tiny seeds that are broadcast, this calculator is not useful because you cannot space them individually.

How do I convert this to metric?

Convert row length to meters (1 ft = 0.3048 m) and seed spacing to centimeters (1 in = 2.54 cm). Then use: total seeds = (row length in cm ÷ spacing in cm) × (100 ÷ germination %). The result will be the same number of seeds.

What if I want to overseed (plant thicker) to allow for thinning?

If you plan to thin, you can enter a smaller spacing than the final spacing. For example, if final spacing is 6 inches but you want to sow at 2 inches and thin, enter 2 inches. The calculator will give you the seeds needed for that denser planting.

Does the calculator account for seed loss due to birds or insects?

No. The germination rate only covers seeds that fail to sprout. If you have heavy pest pressure, you may want to reduce the germination rate further (e.g., use 70% instead of 85%) to compensate. Alternatively, use row covers or other protective measures.

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in l | Row length | ft | 20 | 0 | 10000
in s | Seed spacing | in | 4 | 0.1 | 120
in g | Germination rate | % | 85 | 1 | 100
out total | Total seeds needed | seeds | ceil(round(l * 12 / s * 100 / g, 6)) | 0
out perft | Seeds per foot | seeds/ft | round(12 / s * 100 / g, 2) | 2
out perhole | Seeds per hole (hill) | seeds | max(1, ceil(round(100 / g, 6))) | 0