Straw Calculator
A straw calculator divides area by 80 sq ft per bale and rounds up: a 50 × 20 ft seeded lawn needs 13 bales of straw, or $117 at $9 per bale.
Straw calculator
A straw calculator divides the area you are covering by the area one bale covers. At 80 sq ft per bale, a 50 × 20 ft lawn of 1,000 sq ft needs 12.5 bales. Bales are bought whole, so the answer rounds up to 13, and at $9 each that costs $117.
The same cover keeps seed in place, holds moisture and slows erosion on bare soil.
The formula in plain words
- Area = length × width.
- Bales = area ÷ 80, rounded up.
- Cost = bales × price per bale.
The calculator has no waste option. Round up is the only margin, and you can change it by using a smaller coverage number if the layer needs to be thicker.
Worked examples
A new lawn, 50 × 20 ft:
- Area: 1,000 sq ft
- Bales: 1,000 ÷ 80 = 12.5, rounded up to 13
- Cost: 13 × $9 = $117
A large field, 80 × 30 ft:
- Area: 2,400 sq ft
- Bales: 2,400 ÷ 80 = 30
- Cost: 30 × $9 = $270
A side yard, 40 × 15 ft:
- Area: 600 sq ft
- Bales: 600 ÷ 80 = 7.5, rounded up to 8
- Cost: 8 × $9 = $72
A slope that needs double thickness, 1,000 sq ft at 40 sq ft per bale:
- Bales: 1,000 ÷ 40 = 25
- Cost: 25 × $9 = $225
Bales by area
| Area | Bales at 80 sq ft | Cost at $9 |
|---|---|---|
| 500 sq ft | 7 | $63 |
| 1,000 sq ft | 13 | $117 |
| 2,000 sq ft | 25 | $225 |
| 5,000 sq ft | 63 | $567 |
Bale size varies by farm and region, and so does coverage. If your bales are smaller, cover less area per bale and order more.
How to spread straw over seed
- Rake the seed in lightly and roll or press it into the soil.
- Break the bale into flakes and fluff it.
- Scatter it evenly by hand. Stand up wind and shake it loose.
- Aim for a layer thin enough that you can still see soil through it.
- Water the area well to settle the straw.
Too thick a layer shades the seedlings, and too thin does not hold moisture. On slopes, pin netting over the straw to keep it from sliding.
What straw does for new seed
- Holds moisture around the seed, so you water less often.
- Shades the soil and keeps it cooler.
- Reduces washout from heavy rain.
- Keeps birds from picking the seed off the ground.
- Breaks down and adds a little organic matter.
For the seed itself, the grass seed calculator finds pounds for a new lawn, and the overseeding calculator covers existing grass.
Timing, buying and storing
Spread straw the same day you seed, or as soon as you can after, because seed left bare is the seed birds eat and rain moves. Buy straw close to the job. Bales stored outside soak up rain and go moldy, so keep them dry under a tarp until you spread them.
The result box says bundles, which here means bales. If your supplier sells by the square bale or by a weighed amount, ask how much area one of theirs covers and replace the 80 with that number.
How to measure
Measure length and width in feet. For irregular beds, divide into rectangles and add. For a slope, measure along the surface, not the flat footprint, since a steep bank has more area than it appears from above.
Common mistakes
- Using hay in place of straw, which brings weed seeds.
- Spreading too thickly. A heavy layer blocks light and smothers seedlings.
- Not securing the straw on a slope or in wind.
- Buying exactly 12.5 bales. Round up and expect to use all the straw.
- Using the straw numbers for garden bed mulch, where pine straw or bark gives a more lasting layer. See the pine straw calculator or the mulch calculator.
Frequently asked questions
How much area does one bale of straw cover for seeding?
The calculator uses 80 sq ft per bale, which is a light covering over new grass seed. A 50 × 20 ft lawn is 1,000 sq ft, so 12.5 bales, rounded up to 13. For a thicker cover on a slope, divide the area by a smaller number, such as 40 sq ft per bale.
What is the difference between straw and hay for seeding?
Straw is the stalks left after grain is harvested. Hay is cut to feed animals and often contains seed heads, so it can bring weeds with it. Use clean straw over seed.
When should I take the straw off?
A light layer usually stays and breaks down as the grass grows. If the straw is thick enough to shade the seedlings, rake it thinner once they are up. You should be able to see bits of soil through the straw.
Should I add extra straw for wind or slope?
Yes. On a slope, use a thicker cover and consider netting or staking it. In windy areas, wet the straw after spreading. Halving the coverage to 40 sq ft per bale doubles the bale count, so 1,000 sq ft takes 25 bales.
How is this different from the pine straw calculator?
Pine straw is pine needles sold in bales for garden beds, where it is used as a mulch about 3 inches deep. Farm straw is used thinly over seed and bare soil. The coverage per bale and the purpose are different, so use the pine straw calculator for beds.
Estimates only. Verify quantities with your supplier before purchasing.