This page has no affiliate links and no product picks — just the math, from university tables.
Seed bags don’t know how big your lawn is, or whether you’re starting bare ground or thickening a thin lawn. Answer three questions below and you’ll get a range in pounds — not a single number pretending to be exact.
Grass Seed Calculator
Advanced: adjust for what’s actually in the bag (optional)
Seed bags aren’t 100% live seed. If your bag’s label lists purity and germination, enter them here and the calculator will adjust upward for you. Leave both blank and it assumes good label-quality seed. Example: a label reading 92% purity and 80% germination means only 73.6% of the bag is live seed, so 10 lbs specified becomes 13.6 lbs of bagged seed.
How the Math Works
Pounds of seed = rate (lbs per 1,000 sq ft) × (lawn area ÷ 1,000). That is the whole formula. The calculator never averages a range into a single number: it carries the low and high ends all the way through, so you see 25–35 lbs, not a misleading 30.
If you enter a bag weight, it rounds the bag count up and shows what’s left over. A 35-lb need in 20-lb bags is 2 bags with 5 lbs left over.
Worked Examples
New lawn, mostly tall fescue, 5,000 sq ft: 5–7 × 5 = 25–35 lbs.
Average Minnesota lawn, mostly Kentucky bluegrass, 19,000 sq ft: 2 × 19 = 38 lbs.
Why You Get a Range, Not One Number
Different universities publish slightly different rates, because the rate depends on what’s in the bag — the more tall fescue in the mix, the higher the rate. This calculator uses the University of Minnesota’s mixture table for new lawns. For thickening a thin lawn, Minnesota publishes no per-species overseeding rate, so it uses Kansas State’s rule instead: about half the new-lawn rate. Late-fall seeding uses Minnesota’s dormant-seeding figure for average mixes, 3–4 lbs per 1,000 sq ft. Those are three different jobs, so don’t merge them into one number.
For timing, see the Minnesota lawn care calendar: the best seeding window runs early August to late September, with a mid-November window for dormant seeding. Late-fall seeding suits bare or thin areas that need thickening, not dense lawns where seed can’t reach the soil.
One label tip: look for purity above 90% and germination above 85%. And keep ryegrass to no more than 10% of a Minnesota mix — it often performs poorly there.
The Full Tables (If You Want to Check the Math)
The calculator above uses these tables. They stay here so the page still answers the question even with JavaScript off.
The University of Minnesota Mixture Table (New Lawns)
| Lawn type | Kentucky bluegrass | Tall fescue | Fine fescue | Rate (lbs/1,000 sq ft) |
|---|---|---|---|---|
| Full sun, regularly watered, high traffic | 100% | – | – | 2 |
| Full sun or some shade, occasional watering, moderate traffic | 10% | 90% | – | 5–7 |
| Some shade, some watering, moderate traffic | 20% | – | 80% | 3–5 |
| Full sun, unwatered, low traffic | – | – | 100% | 3–6 |
| Full sun, unwatered, moderate traffic | – | 100% | – | 7–10 |
| Some shade, unwatered, low traffic | – | – | 100% | 3–6 |
Penn State Single-Species Table (Pennsylvania Guidance, for Comparison)
| Species / mixture | Rate (lbs/1,000 sq ft) |
|---|---|
| Turf-type tall fescue, 100% | 6–8 |
| Kentucky bluegrass, 100% | 2–3 |
| Perennial ryegrass, 100% | 4–5 |
| Kentucky bluegrass + perennial ryegrass (80–90 / 10–20) | 2–3 |
| Kentucky bluegrass + fine fescues + perennial ryegrass (40–60 / 20–40 / 10) | 3–4 |
| Fine fescues, 100% (partial or full shade) | 4–5 |
| Rough bluegrass, 100% (full shade) | 2–3 |
| Overseeding / renovation: perennial ryegrass, 100% | 4–6 |
Penn State also warns that seeding too heavily can cause disease and mower scalping, while seeding too lightly leaves thin stands and weeds — which is why this calculator shows ranges and warns when adjustments push a total above the top of the published range.
What This Calculator Does Not Do
It covers cool-season seed only — no bermuda, zoysia, or buffalograss, no sod, plugs, or sprigs, and no prices or cost estimates. For feeding after seeding, see the fertilizer calculator; for whether to aerate before or after overseeding, see should you aerate before or after overseeding; and for the first mow after the work, see how soon you can mow after aerating.
Sources
- University of Minnesota Extension, “Buying turfgrass seed for Minnesota lawns” (reviewed 2025; fetched in full Oct 29, 2026): https://extension.umn.edu/lawns-and-landscapes-minnesota/buying-turfgrass-seed-minnesota-lawns
- University of Minnesota Turfgrass Science, “Consider dormant seeding your lawn this fall” (undated repost; fetched in full Oct 29, 2026): https://turf.umn.edu/news/consider-dormant-seeding-your-lawn-fall
- Penn State Extension, “Lawn Establishment” (fetched in full Oct 29, 2026): https://extension.psu.edu/lawn-establishment
- Purdue Turf, “Rejuvenating Turf in 2011: Part I” (2011; fetched in full Oct 29, 2026): https://turf.purdue.edu/rejuvenating-turf-in-2011-part-i/
- Kansas State Research and Extension, Cottonwood District, “Fall Lawn Seeding Tips” (fetched in full Oct 30, 2026): http://cottonwood.k-state.edu/news_media/2019-ag-news-articles/column%20Fall%20Lawn%20Seeding%20Tips.pdf
