Landscape material calculator: mulch, sod, and seed

How landscape material quantities come off the plan

Three numbers carry most of a landscape material bid: mulch or topsoil volume in cubic yards, sod area in square feet and pallets, and seed weight in pounds. All three start the same way, as an area measured off the planting plan and a depth or an application rate read out of the specification.

Bed areas are measured off the planting sheets as polygons, one per bed or one per bed type, then summed by spec depth. That last part is where the takeoff goes wrong. A 3 inch mulch layer and a 6 inch amended planting soil layer over the same bed are two separate volumes, not one, and if the planting details call for a different depth in shrub beds than in perennial beds you carry them as separate lines. Lawn area is the net turf area, which means beds, walks, pads, and the building footprint come out of the gross site area before you price a square foot of sod or a pound of seed.

The formulas

Volume (cy) = area (sf) x depth (in) / 324

Sod to buy (sf) = net lawn area (sf) x (1 + cutting waste / 100)

Pallets = sod to buy (sf) / coverage per pallet (sf), rounded up

Seed (lb) = area (sf) / 1,000 x rate (lb per 1,000 sf)

Bags = seed (lb) / bag size (lb), rounded up

Where the 324 comes from

Do not take 324 on faith. Derive it once and you will never mistrust it again. You have an area in square feet and a depth in inches, and you want cubic yards.

• Turn the depth into feet: depth (in) / 12 = depth (ft).
• Multiply by the area to get cubic feet: area (sf) x depth (ft) = volume (cf).
• Turn cubic feet into cubic yards: a yard is 3 ft, so a cubic yard is 3 x 3 x 3 = 27 cf, and volume (cf) / 27 = volume (cy).

Stack those and the two divisions collapse into one, because dividing by 12 and then by 27 is the same as dividing by 12 x 27, which is 324. So area x depth / 324 gives cubic yards directly.

The same constant gives you a field check. One cubic yard spread 1 inch deep covers 324 sf, so at 3 inches it covers 324 / 3 = 108 sf, and at 2 inches it covers 324 / 2 = 162 sf. If a supplier tells you a yard of mulch covers 100 square feet, they are quoting you a 3 inch spread.

Sod pallet coverage and seed rate are not universal numbers

Two of the inputs above are the ones estimators get wrong by copying a figure off the internet, which is why this calculator makes both of them editable fields rather than baked-in constants.

Pallet coverage. A sod pallet is not a standard unit. Coverage depends on the grower, on the slab size they cut, and on whether you are buying hand slabs or big rolls. Across suppliers it runs roughly 400 to 700 sf per pallet. The calculator opens at 450 sf, which sits at the low end of that band, so it errs toward more pallets rather than fewer. It is not a standard and it is not a recommendation. Replace it with the coverage printed on your supplier quote. On a 40,000 sf lawn the difference between a 450 sf pallet and a 700 sf pallet is more than 30 pallets.

Seed rate. Rate is species-driven and the spread between species is large. Published cooperative extension turfgrass seeding tables give new-seeding rates in pounds per 1,000 sf of roughly 6 to 8 for tall fescue, 2 to 3 for Kentucky bluegrass, 7 to 9 for perennial ryegrass, 4 to 5 for fine fescue, and 1 to 2 for hulled bermudagrass. Overseeding an existing stand is commonly about half the new-seeding rate. Region, seed lot, and the landscape specification all move the figure, so the spec section and the label on the bag are the authorities, not a default in a web tool. Spreader overlap and the extra pass along edges are normally carried by pricing at the top of the species range rather than by adding a separate waste percentage on top.

When the plan count and the plant schedule disagree

Here is the part that only shows up once you have priced planting work. The count of symbols on the planting plan and the quantities in the plant schedule frequently do not match. A designer relocates three trees in a revision, updates the plan, and the schedule quantity column does not follow. Or the schedule is right and a cluster of shrubs got pasted twice on the plan.

The schedule usually governs, because it is the document that carries species, size, container or balled and burlapped, and root condition, and it is what the specification and the submittal process point at. But usually is not always, and the gap is not yours to close with a guess. Count both, note the delta by species and by size, and put it in an RFI before bid. Price the plan count when the schedule is lower and you have padded yourself out of the job. Price the schedule count when the plan count is higher and you install the difference on your own dollar. Neither is a rounding error when a 36 inch box tree costs many multiples of a 3 gallon shrub.

Topsoil is a scope boundary question before it is a volume

The volume math tells you how many cubic yards of topsoil the beds and the lawn need. It does not tell you what those cubic yards cost, because that depends on where the soil comes from, and that is a scope question rather than a material calculation.

On a site with an earthwork contractor, the topsoil stripped at the start of the job is often stockpiled on site and turned over to the landscape contractor. Then your cost is loading, moving it within the site, screening it if the spec requires that, and amending it. On a site with no stockpile, or a stockpile the earthwork contractor has already priced into their own restoration, or a specification that requires imported screened topsoil to a stated gradation regardless of what is available, you are buying and trucking in every cubic yard. Identical volume, very different money.

So before you price soil, settle three things in the documents: whether the earthwork scope includes stripping and stockpiling topsoil for reuse, who owns the stockpile, and whether the planting spec accepts site material with amendment or requires imported topsoil. If the drawings and specifications do not answer it, that is another RFI, and it is a bigger one than the plant count.

What the clean quantity misses

The geometric volume is the starting point, not the purchase order.

• Settlement and over-spread. Crews spread deeper than spec at bed edges and around tree rings, mulch settles, and material spills at the tailgate. Shops carry somewhere in the 5 to 15 percent band on mulch and soil. The calculator opens at 10 percent because it sits inside that band, not because it is a standard. Use the number your own jobs have produced.
• Cutting waste on sod. A rectangular lawn cuts with very little waste. Curved beds, tree islands, and irregular edges push it up, commonly to 10 percent or more.
• Rounding to the delivery unit. You cannot buy 22.3 cubic yards of bulk mulch or 21.4 pallets of sod. Everything rounds up to whole bags, whole pallets, and whole truckloads, and on a small job that rounding is a real percentage of the line.
• Tree pits and specimen backfill. A tree pit backfilled with amended soil is a volume per tree taken off the planting detail. It is not part of the bed area sweep and it is easy to leave out entirely.
• Access and handling. Whether the truck can back to the beds or the material has to be barrowed from a staging area is a labor number, and on a tight urban site it can exceed the material number.

The two things that turn a profitable landscape bid into a loss

Both of these live after substantial completion, which is exactly why they get missed at bid time.

The maintenance and establishment period. Landscape specifications routinely require the contractor to water, mow, weed, and maintain the planting for a stated period after substantial completion, often 60 or 90 days, sometimes a full growing season, and sometimes until the owner formally accepts the work. Read that last clause carefully, because it is duration risk rather than installation cost. If the general contractor's schedule slips and your planting goes in late in the season, or acceptance drags while punch items close out elsewhere on the site, the period stretches and every extra week is crew time and trips you did not price. Price it as a duration times a crew rate times a trip count, then read the project schedule to see how long that duration could realistically become.

Plant warranty and replacement. Warranty on plant material is commonly one year from substantial completion, sometimes two on trees, and it obliges you to replace what fails. Whether it obliges you to replace a given plant once or to keep replacing it until it survives is a contract question worth asking before you bid, not after. Replacement is also not just the plant. It is the plant, the labor to remove the dead one, the protection or access needed to get equipment back onto a finished site, and the trip. On top of that you are exposed to failure causes you do not control, including owner irrigation that gets shut off, drought, and vandalism, so the clauses to find are who waters during the warranty period and what happens if the irrigation system is not operated. A warranty allowance set as a flat percentage of plant material is a guess. One built from your own historical replacement rate by species and size is an estimate.

Worked example

These are the calculator's own defaults, so every step below can be checked against the output above.

Mulch. Beds total 2,160 sf at 3 inches of mulch. Volume = 2,160 x 3 / 324 = 6,480 / 324 = 20.00 cy net. Add 10 percent for settlement and over-spread: 20.00 x 1.10 = 22.00 cy to order. In bulk supersacks of 1 cy that is 22 bags. Bagged instead: 22.00 cy x 27 = 594 cf, and at 2 cf per bag, 594 / 2 = 297 bags. The contrast is worth looking at, because 297 bags is a labor and disposal number as much as a material number.

Sod. Net lawn area 9,000 sf with 5 percent cutting waste: 9,000 x 1.05 = 9,450 sf of sod. At 450 sf per pallet, 9,450 / 450 = 21 pallets exactly. At 700 sf per pallet the same lawn is 13.5 pallets, which you buy as 14.

Seed. The same 9,000 sf lawn seeded with tall fescue at 6 lb per 1,000 sf: 9,000 / 1,000 = 9.0, and 9.0 x 6 = 54 lb of seed. At 50 lb per bag that is 2 bags, with most of the second bag left over.

From quantities to a priced bid

Every number on this page is a quantity. The bid is those quantities against your own unit costs, plus plant material priced by species and size off the schedule, plus irrigation, plus the establishment period and the warranty exposure described above. That last third is where landscape bids are actually won and lost, and none of it comes out of an area times a depth.

Ruh reads the drawing set, measures the scope, and prices measured quantities against your own price book, with every line traceable to the sheet it came from. For how that applies to planting work see landscape estimating software, and for the bid mechanics around scope, schedule, and warranty see how to bid landscaping as a subcontractor.