1839
Seaweed mulch chart
Put your bed area, seaweed mulch depth and waste allowance in: 1400 sq ft at 2 inches with 10% waste needs 1,540.00 sq ft, 9.51 cubic yards exact — order 10 cubic yards.
★ CONSTRUCTION · MULCH · SEAWEED MULCH CHART
Seaweed Mulch Chart: 1400 Sq Ft, 2 Inches, Order 10 Yards
On the defaults — a 1400 square foot bed at 2 inches deep with a 10% waste allowance — you need 1,540.00 square feet of cover, 9.51 cubic yards exact, so order 10 cubic yards. This is the SEAWEED version — the mulch chart for seaweed, which adds minerals and breaks down quickly — the rice-hull-mulch-chart page is the RICE HULL version, the hay-mulch-chart page is the HAY version, and the mulch-chart page is the GENERAL version for any loose mulch.
What does 9.51 cubic yards of seaweed mulch mean?
It means a 1400 square foot bed, once the 10% waste allowance is added, needs 1,540.00 square feet of cover at 2 inches deep — 256.67 cubic feet, which is 9.51 cubic yards. Because mulch is sold by the whole yard, you order 10 cubic yards: the extra 0.49 yard covers settling and the thin spots every bed has. At 2 inches, one cubic yard covers 162.0 square feet, so the same bed at 1 inch would need only 4.75 yards, and at 3 inches it would need 14.26 yards.
Output · formula · meaning
| Output | Formula | What it means |
|---|---|---|
| Area needed | area × (1 + waste ÷ 100) | 1,540.00 sq ft — 1400 × 1.10. |
| Exact volume | area needed × depth ÷ 324 | 9.51 cubic yards — 1,540.00 × 2 ÷ 324. |
| Order quantity | round exact volume up to a whole yard | 10 cubic yards — the next whole yard above 9.51. |
| Coverage per yard | 324 ÷ depth | 162.0 sq ft per yard — 324 ÷ 2. |
| Area behind a target volume | target volume × 324 ÷ depth ÷ (1 + waste ÷ 100) | 1400 sq ft — 9.51 × 324 ÷ 2 ÷ 1.10, rounded. |
| Depth behind a target volume | area needed × depth ÷ 324, solved for depth | 2 inches — the depth that turns 1,540.00 sq ft into 9.51 yards. |
| Waste behind a target volume | target volume × 324 ÷ depth ÷ area − 1, as a percent | 10% — the allowance that turns 1400 sq ft into 1,540.00 sq ft. |
Three things to check before you trust the number
First, measure the bed honestly: length times width for each bed, added together, with L-shaped beds split into rectangles. A guessed area moves the order by the same percentage as the guess. Second, keep the depth honest: seaweed dries and thins quickly, so a layer spread at 2 inches may sit closer to 1 inch within weeks — if you want 2 inches after settling, spread a little deeper and say so. Third, do not skip the waste allowance on seaweed: it washes in heavy rain, dries and thins in sun and settles into dips, so the 10% allowance is the difference between finishing the bed and running short with the truck already gone.
Worked example
Area 1400 sq ft, depth 2 inches, waste 10%. Area needed: 1400 × 1.10 = 1,540.00 sq ft. Exact volume: 1,540.00 × 2 ÷ 324 = 9.51 cubic yards. Order: round 9.51 up to 10 cubic yards. Drop the waste to 0% and the exact volume falls to 8.64 yards, order 9; drop the depth to 1 inch and it falls to 4.75 yards, order 5. Depth moves the answer faster than waste does, because every inch adds a full layer across the whole bed.
Seaweed mulch lookup table
Every row below applies 10% waste to the area first, then divides by 324: yards = area needed × depth ÷ 324, rounded up to the next whole yard for the order. Find your bed size and depth, read across, and order the last column.
| Area (sq ft) | Depth (inches) | Area needed (sq ft, 10% waste) | Exact (cubic yards) | Order |
|---|---|---|---|---|
| 250 | 2 | 275.00 | 1.70 | 2 cubic yards |
| 250 | 3 | 275.00 | 2.55 | 3 cubic yards |
| 500 | 2 | 550.00 | 3.40 | 4 cubic yards |
| 500 | 3 | 550.00 | 5.09 | 6 cubic yards |
| 750 | 2 | 825.00 | 5.09 | 6 cubic yards |
| 750 | 3 | 825.00 | 7.64 | 8 cubic yards |
| 1000 | 2 | 1,100.00 | 6.79 | 7 cubic yards |
| 1000 | 3 | 1,100.00 | 10.19 | 11 cubic yards |
| 1200 | 3 | 1,320.00 | 12.22 | 13 cubic yards |
| 1400 | 2 | 1,540.00 | 9.51 | 10 cubic yards |
| 1500 | 2 | 1,650.00 | 10.19 | 11 cubic yards |
| 1500 | 4 | 1,650.00 | 20.37 | 21 cubic yards |
| 1750 | 3 | 1,925.00 | 17.82 | 18 cubic yards |
| 2000 | 3 | 2,200.00 | 20.37 | 21 cubic yards |
| 2500 | 2 | 2,750.00 | 16.98 | 17 cubic yards |
| 3000 | 3 | 3,300.00 | 30.56 | 31 cubic yards |
Every branch, checked
A 1400 square foot bed at 2-inch depth with 0% waste gives 8.64 cubic yards exact, order 9 cubic yards. The same bed at 3-inch depth with 10% waste gives 14.26 cubic yards exact, order 15 cubic yards. A 1300 square foot bed at 2-inch depth with 10% waste gives 8.83 cubic yards exact, order 9 cubic yards. A 1500 square foot bed at 2-inch depth with 10% waste gives 10.19 cubic yards exact, order 11 cubic yards. Each branch changes exactly one input, so the difference from 9.51 isolates that input.
The reverses, worked backwards
The area behind 9.51 cubic yards is 1400 sq ft: at 1300 sq ft the figures are 8.83 cubic yards exact, order 9 cubic yards, and at 1500 sq ft they are 10.19 cubic yards exact, order 11 cubic yards. The depth behind 9.51 cubic yards is 2 inches: at 1 inch the figures are 4.75 cubic yards exact, order 5 cubic yards, and at 3 inches they are 14.26 cubic yards exact, order 15 cubic yards — one inch either way moves the order by about 5 yards. The waste behind 9.51 cubic yards is 10%: at 5% the figures are 9.07 cubic yards exact, order 10 cubic yards, and at 15% they are 9.94 cubic yards exact, order 10 cubic yards — waste moves the exact volume but leaves the order at 10 yards in both cases.
What the defaults assume
The defaults assume a flat 1400 square foot bed, a uniform 2-inch layer, and a 10% waste allowance. Real seaweed beds are rarely flat: slopes shed mulch downhill, paths and tree trunks eat into the area, and seaweed thins as it dries, so measure the planted area only and keep the waste allowance on sloped ground. Zero square feet is the honest edge: 0.00 cubic yards exact, order 0. A depth of zero or below, a negative area, or a negative waste allowance is rejected, because none of them describes a real bed.
Who uses this
A gardener mulching a large vegetable bed with seaweed: the 1400 square foot headline is a big kitchen-garden bed, and the table covers everything from a 250 square foot border to a 3000 square foot orchard floor. A landscaper quoting a seaweed job: the waste column protects the quote, and the order column is the number given to the supplier. A homesteader spreading bulk seaweed on paths: the 2-inch rows are the path depths, and the 3-inch rows are the bed depths. A community garden coordinator splitting a bulk delivery: each plot reads its own row, and the orders add up to the truckload.
Accuracy & limitations
The arithmetic is exact for the inputs entered; the judgement is in the inputs. A guessed area, a depth measured before settling, or a skipped waste allowance will each move the answer by exactly the amount of the error, every load. The model does not include salt residue in soil, compaction over the season, or delivery minimums — a supplier may sell only in whole yards or charge extra below a minimum, so confirm the order quantity with the supplier. This page is a calculation tool, not landscaping advice.
Cite this calculator
Seaweed mulch 1400 sq ft at 2-inch depth with 10% waste needs 1,540.00 sq ft, 9.51 cubic yards exact, order 10 yards. Free calculator, plus 16-row table. Source: Bright Side Kit, https://brightoolbox.com/seaweed-mulch-chart/, accessed 30 October 2026 (2026-10-30).
Frequently asked questions
Why does the table apply waste to the area first?
Because waste is lost cover: spillage, wind and uneven ground mean you need more covered area than the bed measures. Adding 10% to the area, then converting to yards, keeps the waste in the same units as the bed. Applying it after the conversion gives the same number here, but the area-first order keeps the table readable.
How deep should seaweed mulch really be?
Two inches is the standard bed layer on this page, and 1 inch suits paths and top-ups. Seaweed breaks down faster than bark, so a 2-inch spread may settle toward 1 inch; if you want a lasting 2-inch layer, spread slightly deeper and expect to top up during the season.
Does seaweed mulch introduce weed seeds?
Seaweed usually carries far less weed seed than hay, so it is a lower-risk mulch for weed seeds; rinse it first if you garden salt-sensitive plants, then use it on beds or paths. This calculator prices volume only and does not judge the gardening choice.
What if my bed is not a rectangle?
Split it into rectangles, measure each, and add the areas before entering the total. A circle uses radius times radius times 3.14. Guessing one number for an irregular bed is the most common reason orders come up short.
Why order 10 yards when the exact figure is 9.51?
Because mulch is sold by the whole yard and you cannot buy 0.51 of a yard from most suppliers. Rounding up also covers settling and thin spots; the 0.49 yard of headroom is cheaper than a second delivery for a shortfall.
Can I use this chart for other mulch types?
The volume math is the same for any loose mulch — area, depth and waste convert the same way — but settling and coverage differ by material. Bark holds its depth longer than seaweed, so use the seaweed rows for seaweed and the matching chart for bark or wood chips.