Seed Packet Yield Calculator

Estimate how many plants you can expect from a single seed packet and how much produce you will harvest, based on packet seed count, germination rate, bed dimensions, and plant spacing.

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Frequently Asked Questions

How do I find the germination rate on a seed packet?
Most seed packets print the germination rate directly on the back, often near the lot number or "packed for" date. It appears as a percentage (e.g., "Germ: 85%"). If yours does not list it, use the federal minimum standards for that crop as a conservative estimate, or check the seed company's website for their lot test results. For packets more than two years old, knock 15–20 percentage points off the labeled rate as a practical adjustment.
What spacing should I use for square foot gardening vs. row gardening?
Square foot gardening uses a grid system that typically allows for tighter spacing than traditional row gardening because there are no walking paths within the bed. A tomato in a traditional row might need 24–36 inches; in a raised square-foot bed you can go 18–24 inches with good support. This calculator uses a simple grid model, which maps directly to square foot and raised-bed methods. For row gardening, enter the within-row spacing in the spacing field and note that row-to-row spacing (usually 18–36 inches) means your actual bed width holds fewer rows than the grid model suggests.
Should I account for thinning when I enter seed count?
Yes, if you are direct-sowing crops that require thinning (carrots, beets, lettuce). In that case, sow at the recommended density (often 2–3 seeds per inch) and enter the final thinned plant count as your target rather than the raw germinated seedling count. The calculator models the final stand, not the initial sow-density. For transplant crops started indoors (tomatoes, peppers, brassicas), enter the expected seedling count after germination — thinning happens in the tray, not the bed.
How accurate is the grocery value estimate?
The grocery value is a planning estimate based on the per-pound price you enter and average yield-per-plant reference data. Actual harvest varies widely by variety, weather, soil fertility, irrigation, and pest pressure. High-production tomato varieties (Sungold, Sweet 100) may produce 8–12 lbs per plant; low-production heirlooms may produce 2–4 lbs. Use the number to set expectations and compare garden ROI across crops — not as a precise harvest guarantee. Re-run the calculator mid-season with your actual plant count and observed yield to get a more accurate projection.

How to Estimate What a Seed Packet Will Produce

Every seed packet tells you the count, but never the full picture. Germination rate, bed size, and plant spacing together determine how many plants you actually end up with — and how much that translates into harvested produce. This calculator works through that math so you can plan your garden before you plant, not after half the bed sits empty.

Plants to Grow = MIN(Seeds × Germination Rate, Bed Capacity)
Bed Capacity = floor(Bed Length ÷ Spacing) × floor(Bed Width ÷ Spacing)
Harvest (lbs) = Plants to Grow × Yield Per Plant
Grocery Value = Harvest × Price Per Pound

Understanding Germination Rate

Germination rate is the percentage of seeds from a packet you can expect to actually sprout under good conditions. Seed packets sold in the US must meet minimum germination standards set by the Association of Official Seed Certifiers — typically 75–90% for common vegetables. Fresh seed from a reputable supplier will often hit the high end; seed stored for more than a year, or kept in a warm humid location, will drop. A packet labeled "80% germination" with 50 seeds produces roughly 40 seedlings. Common reference rates to use when you do not have packet data:

  • Tomatoes, peppers: 80–90%
  • Lettuce, spinach, kale: 80–85%
  • Carrots, parsnips: 65–75% (lower than most; sow more thickly)
  • Beans, peas: 80–90%
  • Brassicas (broccoli, cabbage): 80–85%
  • Cucumbers, squash, melons: 90–95%
  • Old seed (>2 years): subtract 15–25% from the above

Matching Seed Count to Bed Capacity

One of the most common planning mistakes is buying a single large packet for a small bed, only to discard hundreds of surplus seedlings — or buying a small packet that leaves a third of the bed bare. The calculator flags both scenarios. Bed capacity is determined by dividing each dimension by the recommended plant spacing and multiplying the grid result. A 4 ft × 8 ft bed with 12-inch spacing holds exactly 32 plants. At 6-inch spacing it holds 128. Spacing recommendations exist for airflow, root competition, and disease prevention — overcrowding to use more seed is a trade-off, not a free gain.

Grocery Value: What Your Garden Is Actually Worth

Translating harvest weight into a grocery equivalent makes garden math concrete. A 4 × 8 bed of tomatoes planted at 24-inch spacing holds 8 plants; at 3 lbs per plant average that is 24 lbs, worth around $48–$72 at typical 2026 grocery prices. Bush beans at 6-inch spacing in the same bed yield 32 plants and 64–96 lbs of beans — roughly $130–$190 in store value. These are planning numbers, not guarantees; actual yield depends on soil, weather, pest pressure, and variety.

Practical Guide for Seed Packet Yield Calculator

The single most useful habit this calculator can build is planning backward from your bed size rather than forward from the packet. Most gardeners buy seeds first and figure out where to plant them later, which is why so many packets end up half-used in a drawer. If you know your bed is 4 × 8 feet and you want to grow tomatoes at 18-inch spacing, you need exactly 12 plants — which means you need 12 viable seedlings, which at 85% germination means starting 15 seeds. One packet of 25 seeds is plenty with seeds left over for next year.

Germination rate has an outsized effect on the math. A crop with 65% germination (common for old carrot seed) produces 33 seedlings from a 50-count packet versus the 43 you would get at 85%. That 10-plant difference can mean a meaningfully underfilled bed. Always check the "packed for" year on the packet — seed companies test and label by calendar year, and a packet labeled 2023 being used in 2026 may be down 20–30 points from its stated rate. Do a quick germination test on paper towels before you commit a whole bed if you are unsure.

The grocery value metric is most useful for choosing between crops when you have limited bed space. Crops with high yield-per-square-foot (bush beans, lettuce, kale, cherry tomatoes) consistently outperform crops with low yield-per-square-foot (melons, pumpkins, sweet corn) on a grocery-value basis. Run this calculator for two or three candidate crops and compare the grocery value per square foot to make space allocation decisions rather than going by intuition.

Review Checklist

  • Check the germination rate and "packed for" date on every packet before entering numbers — old seed needs a downward adjustment.
  • Compare bed capacity to expected seedling count before sowing; buy a second packet or plan to fill gaps with a companion crop if the packet falls short.
  • Use the surplus seedling count to plan container starts, share with neighbors, or schedule a second sowing for succession planting.
  • Re-run the calculator with your actual end-of-season plant count and harvested weight to calibrate your yield-per-plant assumptions for next year.