How We Calculate
We want you to be able to check our math. Here's every number our calculators use, where it comes from, and what it doesn't cover.
Volume
Every calculator converts your measurements to cubic feet, then divides by 27 to get cubic yards. Inches are divided by 12. Circles use π × r². Steps are figured as stacked blocks, so the bottom step is one riser tall, the next is two, and so on.
The extra allowance
We add a percentage you choose: 10% by default for concrete and bulk materials, and 5–15% for pavers depending on the pattern. It covers spillage, uneven grades, forms that bow, settling and compaction. The exact volume, with no extra, is always shown too.
Concrete bag yields
| Bag | Yield (cu ft) |
|---|---|
| 40 lb | 0.3 |
| 60 lb | 0.45 |
| 80 lb | 0.6 |
These are the yields printed on standard concrete-mix bags from the major brands. Specialty mixes (high-strength, fast-setting, crack-resistant) can yield a bit differently. Check the bag.
Ready-mix costs
Truck orders are rounded up to the nearest ¼ yard. If the order is under the short-load minimum (6 yd by default), a flat short-load fee ($100 by default) is added. Plants vary a lot. Some charge per missing yard, and some add fuel, environmental or Saturday fees. You can change every one of these numbers in the calculator.
Material weights
| Material | Tons per yd³ (dry, loose) |
|---|---|
| Crushed stone (#57 / #411) | 1.35 |
| Crusher run / road base | 1.5 |
| Pea gravel | 1.4 |
| Decomposed granite | 1.3 |
| River rock (1–3") | 1.3 |
| Shredded hardwood mulch | 0.3 |
| Pine bark nuggets | 0.25 |
| Rubber mulch | 0.55 |
| Screened topsoil | 1.1 |
| Garden soil / soil-compost blend | 0.9 |
| Compost | 0.6 |
| Mason / play sand | 1.35 |
| Concrete sand (paver bedding) | 1.35 |
| Fill dirt | 1.2 |
These are typical figures. Moisture can add 10–30%, and different quarries' stone varies.
Truck trips
A trip is limited by whichever runs out first: the vehicle's payload or its bed volume. We use conservative typical payloads. Your truck's actual payload is on the sticker in the driver's door jamb.
| Vehicle | Payload used | Bed volume (level) |
|---|---|---|
| Compact pickup (Tacoma, Ranger) | 1,200 lb | 1.3 yd³ |
| Full-size ½-ton pickup (F-150, Silverado 1500) | 1,700 lb | 2 yd³ |
| ¾-ton pickup (F-250, 2500) | 2,800 lb | 2.2 yd³ |
| 5×8 single-axle utility trailer | 2,000 lb | 1.5 yd³ |
Wheelbarrow loads are capped at 6 cu ft or 300 lb, whichever comes first.
Prices
Default prices are national typical ranges from retailer listings and published cost guides, last checked October 2026. They are not quotes. Local prices can be well above or below them, so type in your supplier's numbers for a real budget.
What these calculators don't do
- They don't design structures. Footing sizes, slab thickness, reinforcement and frost depth must follow your local building code, and structural work should be designed by a qualified professional.
- They don't account for site-specific losses like extremely soft soil or very irregular excavations.
Found an error? Tell us and we'll fix it.