Every calculator on Home And Yard Calc uses standard geometry plus typical material values. This page shows the formulas, the values we use and how we check them, so you can see exactly where each number comes from.
1. Area
- Rectangle: length × width
- Circle: 3.1416 × radius × radius (the radius is half the diameter)
- If you already know the area, you can enter it directly.
2. Volume
Volume is area × depth, with every measurement in the same unit.
- US units: cubic feet = square feet × depth in inches ÷ 12. Cubic yards = cubic feet ÷ 27.
- Metric: cubic metres = square metres × depth in centimetres ÷ 100.
Example: a 20 ft × 10 ft area, 3 inches deep, is 200 × 3 ÷ 12 = 50 cubic feet, which is 50 ÷ 27 = 1.85 cubic yards.
3. From volume to weight
Many suppliers sell by the ton, so we convert volume to weight: tons = cubic yards × weight per cubic yard. These are the typical values our calculators use:
| Material | US tons per cubic yard | Tonnes per cubic metre |
|---|---|---|
| Hot mix asphalt (compacted) | 1.96 | 2.33 |
| Crusher run / dense grade, Class II road base | 1.55 | 1.84 |
| #411 (#57 with stone dust) | 1.45 | 1.72 |
| Pea gravel | 1.40 | 1.66 |
| Stone dust / screenings | 1.40 | 1.66 |
| Marble chips, crushed granite | 1.40 | 1.66 |
| Fill sand | 1.40 | 1.66 |
| #57 and #8 crushed stone | 1.35 | 1.60 |
| All-purpose or concrete sand | 1.35 | 1.60 |
| River rock, beach pebbles | 1.30–1.35 | 1.54–1.60 |
| #3 crushed stone | 1.30 | 1.54 |
| Decomposed granite | 1.30 | 1.54 |
| Masonry sand, play sand | 1.30 | 1.54 |
| Fill dirt | 1.30 | 1.54 |
| Screened topsoil | 1.10 | 1.31 |
| Garden soil blend | 1.00 | 1.19 |
| Lava rock | 0.60 | 0.71 |
| Compost | 0.55 | 0.65 |
Stone, soil and sand values are for dry, loose material. Asphalt is compacted hot mix, at about 145 pounds per cubic foot. Mulch and raised bed soil are bought by volume, so those calculators give cubic yards, cubic feet and bags rather than tons.
Real weights vary with moisture, rock type and the quarry. Wet material weighs more. If your supplier gives you their own figure, choose “Custom weight” and enter it.
4. Extra for settling, compaction and waste
Each calculator adds a default buffer that you can change: 5% for decorative rock, asphalt, sod, artificial turf trimming and rebar cutting; 10% for gravel, pea gravel, sand, mulch, raised bed soil and concrete; and 15% for topsoil, crushed stone, driveway base layers and turf base.
5. Bags
Bag sizes follow what stores usually sell: 0.5 cubic feet for gravel, stone and sand (about 50 lb), 0.75 cubic feet for topsoil, 1.5 cubic feet for raised bed soil and 2 cubic feet for mulch. Metric results use 25 kg bags for stone and sand, and litre bags for soil and mulch. Bag counts are always rounded up.
6. Rounding
Results are shown rounded for easy reading. Calculations use the full, unrounded numbers.
7. How we check the calculators
Before a calculator goes live, we run worked examples through it and compare the results with the same sums done by hand. When we change a formula or a value, we check it again and update the date on that page.
8. How this content is written
Some explanatory text on this site is drafted with the help of AI tools, then reviewed and edited by a person. Formulas and material values are checked by hand.
9. Lawn calculators
Sod: pieces = lawn area × (1 + extra) ÷ area of one piece. Common sizes are 16 × 24 in slabs (2.67 sq ft), 18 × 24 in slabs (3 sq ft) and 2 × 5 ft rolls (10 sq ft). Pallets are set to 450 sq ft by default; real pallets usually hold 400 to 500 sq ft depending on the farm, so you can change it.
Grass seed: pounds of seed = lawn area ÷ 1,000 × seeding rate. Default rates are typical values from university extension guides, including Penn State, NC State and the University of Florida. Where a guide gives no overseeding figure, we use roughly half the new-lawn rate. Seed blends differ, so the rate on your bag always comes first.
| Grass | New lawn (lb per 1,000 sq ft) | Overseeding (lb per 1,000 sq ft) |
|---|---|---|
| Tall fescue (turf-type) | 7 (range 6–8) | 4 (range 3.5–4.5) |
| Perennial ryegrass | 6 (range 5–7) | 4 (range 3–5) |
| Bahiagrass | 7 (range 5–10) | 4 (range 3–5) |
| Fine fescue | 4.5 (range 4–5) | 2.5 (range 2–3) |
| Kentucky bluegrass | 2.5 (range 2–3) | 1.5 (range 1–2) |
| Bermudagrass (hulled seed) | 1.5 (range 1–2) | 0.75 (range 0.5–1) |
| Zoysiagrass | 1.5 (range 1–2) | 0.75 (range 0.5–1) |
| Centipedegrass | 0.4 (range 0.25–0.5) | 0.25 |
Artificial turf: turf comes in rolls of a fixed width (usually 15 ft, sometimes 12 ft) cut to length. For a rectangle, the calculator works out how many strips cover the area in each direction and picks the layout with the fewest seams, unless that would use more than 10% extra turf. Infill = area × infill rate (1.5 lb per sq ft by default). Base = area × base depth (3 in by default) plus compaction, converted to tons with the weights above.
10. Concrete, footings and rebar
Concrete bags: bags = cubic feet ÷ the yield of one bag. We use typical yields for premixed concrete:
| Bag | Yield | Bags per cubic yard |
|---|---|---|
| 80 lb | 0.60 cu ft | 45 |
| 60 lb | 0.45 cu ft | 60 |
| 50 lb | 0.375 cu ft | 72 |
| 40 lb | 0.30 cu ft | 90 |
Metric bag yields (about 11.7 litres for 25 kg and 9.4 litres for 20 kg) are worked out from the same yield per pound. Each brand prints its own yield on the bag.
Columns and footings: volume = 3.1416 × radius × radius × depth. When a post sits in the concrete, its square cross-section is taken away first.
Rebar: bars are kept a set distance from the edges and spaced evenly both ways. Where a bar is longer than one stick, the pieces overlap by 40 bar diameters, a common rule of thumb. Weights per foot are standard values: #3 0.376 lb, #4 0.668 lb and #5 1.043 lb.
11. Cost calculators
Our cost calculators don’t fill in prices, because concrete, asphalt and labor prices vary widely by region and season. You enter prices from your own suppliers and contractors, and the calculator works out the quantities and adds everything up. Any example prices on our pages are for illustration only.
12. Found an error?
Email homeandyardcalc@gmail.com with the calculator link and the numbers you used. We fix confirmed errors and note the change on the page.