How we calculate
Last updated October 2026
Every calculator runs the same small set of formulas, written once and covered by automated tests, so the numbers in a page's tables always match its calculator. Results are planning estimates — check measurements, local codes and supplier figures before you buy or build.
Volume
cubic feet = area (sq ft) × depth (ft) · cubic yards = cubic feet ÷ 27 · m³ = cubic feet × 0.0283
Areas: rectangle = length × width; circle = π × (diameter ÷ 2)²; triangle = base × height ÷ 2. Any extra percentage (waste, settling, compaction) is applied to the final volume.
Weight
Tons = cubic yards × pounds per cubic yard ÷ 2,000 (US short tons). Metric tonnes use 1,000 kg. Typical dry, loose weights we use:
| Material | Typical lb/yd³ | Range |
|---|---|---|
| Wood / bark mulch | 600 | 400–800 |
| Pine bark nuggets | 500 | 400–700 |
| Compost | 1,200 | 800–1,600 |
| Topsoil (screened) | 2,200 | 2,000–2,600 |
| Fill dirt | 2,400 | 2,000–2,700 |
| Garden soil / soil blend | 1,800 | 1,400–2,200 |
| Gravel (general) | 2,800 | 2,600–3,000 |
| Crushed stone / #57 stone | 2,700 | 2,500–2,900 |
| Pea gravel | 2,700 | 2,500–2,900 |
| River rock | 2,700 | 2,500–2,900 |
| Crushed limestone | 2,700 | 2,500–2,900 |
| Decomposed granite | 2,800 | 2,600–3,000 |
| Road base / crusher run | 3,000 | 2,800–3,200 |
| Lava rock | 1,100 | 900–1,500 |
| Sand | 2,700 | 2,500–3,000 |
| Hot-mix asphalt (compacted) | 3,915 | 3,780–4,050 |
| Asphalt millings (recycled) | 2,500 | 2,300–2,800 |
| Concrete | 4,050 | 3,900–4,100 |
Moisture, grading and compaction change real weights by 10–30%. Every calculator lets you type your supplier's figure.
Bags
Bag counts are volume ÷ bag size, rounded up. Premixed concrete yields (per standard US bag):
- 40 lb bag → 0.3 ft³
- 50 lb bag → 0.375 ft³
- 60 lb bag → 0.45 ft³
- 80 lb bag → 0.6 ft³
Carpentry and walls
- Board feet = thickness (in) × width (in) × length (ft) ÷ 12, on nominal sizes.
- Stairs follow the 2021 International Residential Code limits (7¾" max riser, 10" min tread) and AWC DCA 6 guidance (5" minimum throat on cut stringers).
- Siding coverage uses each product's exposure × length; 1 square = 100 sq ft.
- Board and batten spreads the battens evenly from edge to edge, choosing the count whose gap is closest to your target.
Heating and cooling
Cooling uses the ENERGY STAR room air conditioner sizing chart and its adjustments (±10% for shade/sun, +600 BTU per person over two, +4,000 BTU for kitchens), scaled for ceilings over 8 ft. Heating uses a climate-zone rule of thumb (30–60 BTU per sq ft). Neither replaces a Manual J load calculation for whole-house equipment.
Costs
Cost ranges are typical 2026 US installed prices, cross-checked against several published 2026 cost guides and public bid data, and rounded to ranges rather than false precision. They're national: high-cost metros often run 20–40% higher. Every cost calculator accepts your own quote per square foot. We review prices at least once a year.
Found a mistake?
Email us — corrections are reviewed and fixed promptly, and the review date at the top of this page changes when we do.