Gravel Calculator for Colorado Drives, Drains and Turnarounds
Enter your project dimensions
Colorado ground gets worked hard. Frost goes about 30 to 36 inches down in much of the state, clay swells when it's wet, and a sunny winter day can thaw a drive that refreezes by dark. Rock that's too thin doesn't last long under that. So before we explain the gravel calculator, here is one full-size example run through it first.
Start here: a 40-foot turnaround, worked out
This is a hypothetical example. Picture an acreage drive that ends in a loop so a truck and trailer can turn around. The plan calls for a circle 40 feet across with 6 inches of compacted Class 6 road base.
- Area. Radius is 20 ft. 3.1416 x 20 x 20 = 1,256.6 sq ft.
- Volume. 1,256.6 x 6 ÷ 12 = 628.3 cu ft.
- Yards. 628.3 ÷ 27 = 23.27 yd³.
- Tons. 23.27 x 1.50 = 34.9 tons.
- With the 5% box. 24.43 yd³ and 36.65 tons.
Order about 37 tons. Put it down in two lifts and compact each one.
Rule of thumb: a 40-ft circle at 6 inches of base is roughly 35 tons. Double the depth and you double the tons.
Entering an acreage drive in the tool
- Pick a shape. Rectangle, Circle, or Multiple areas (up to 5).
- Enter dimensions in feet. Length and width, or a diameter.
- Enter depth in inches. Anything from 0.25 to 24.
- Pick the material. The weight changes with it.
- Decide on the 5%. "Add 5% extra for compaction & spillage." Tick it for base.
- Calculate. Read cubic yards, tons and cubic feet.
- Want it in writing? Hit Email my quote.
Odd shape? Break it into up to five rectangles and circles that don't overlap. A drive with a turnaround at the end is two entries.
Class 6 weight factors and two more Front Range jobs
Cubic feet is length x width x depth, with depth in inches divided by 12. Cubic yards is cubic feet ÷ 27. Tons is yards x the material's weight factor:
| Pick in the dropdown | Weight, lb/yd³ | Factor, t/yd³ |
|---|---|---|
| Driveway / walkway gravel | ≈ 2,800 | 1.40 |
| Pea gravel, 3/8" | ≈ 2,800 | 1.40 |
| Crushed stone, #57 or 3/4" | ≈ 2,800 | 1.40 |
| Crusher run / road base | ≈ 3,000 | 1.50 |
| River rock, 1-3" | ≈ 2,700 | 1.35 |
Class 6 is the road base product, so it runs at 1.50. Clean stone is lighter per yard because it has open voids. Base has fines packed into those voids.
Example: French drain along a foundation
Also hypothetical. The trench is 50 ft long and 18 inches wide, filled 18 inches deep with #57 stone. Enter width as 1.5 ft. 50 x 1.5 x 18 ÷ 12 = 112.5 cu ft. ÷ 27 = 4.17 yd³. x 1.40 = 5.83 tons. With 5%, that's 6.1 tons. The pipe takes up a little room, and that's your margin.
Example: filling a low spot in the yard
A dip in a gravel parking area, 15 x 12 ft, averaging 3 inches low. Fill it with Class 6. 15 x 12 x 3 ÷ 12 = 45 cu ft. ÷ 27 = 1.67 yd³. x 1.50 = 2.5 tons. If the regrade is soil, not rock, use the dirt calculator instead.
Extra Class 6 for lifts and low spots
Rule of thumb: tick the 5% for anything you'll compact. Untick it for loose decorative rock.
- Measuring a low spot by eye? Use the deepest spot, not the average.
- Clay subgrade that's still soft from snowmelt? Round your dimensions up too.
- In between two ton figures? For base, go up.
Delivery is arranged at checkout by ZIP code. The truck needs a clear, firm dump spot. Frozen or muddy ground in early spring may not hold it.
Picking the rock
- Drives, pads, turnarounds: Class 6 road base, compacted in lifts. Add driveway gravel on top if you want a loose finish.
- Drains and foundations: clean stone with no fines, like #57 or Drain Rock. Water has to move through it.
- Xeric beds and borders: river rock or pea gravel. Rounded stone rolls under tires, so keep it off the drive.
Why depth and drainage matter so much here:
- Water gets into the base.
- It freezes and expands, sometimes several times in one week at altitude.
- It thaws, and the base is looser than it was.
- Traffic pushes the loose rock into ruts.
The fix is to keep water out and give the rock enough thickness to lock together. Crown the drive so it sheds snowmelt. Compact the base at the right moisture, not bone-dry. Don't let a swale dump runoff across the surface. If a slope sends water toward the drive, catch it first with a drain lined with clean stone.
Rule of thumb: if a spot ruts every spring, it needs better drainage before it needs more rock.
Timing matters too. Base work goes most smoothly from late spring through fall. Frozen ground and snowpack at altitude won't compact.
Road base delivery out on the acreage
Run your numbers, then go to the product page to choose a date and quantity. Check delivery for your area on the Colorado locations page. Questions about your base depth? Ask through the contact page.
Common questions
I'm topping up an old drive, not starting from dirt. What depth do I enter?
For a top-up, enter only the new layer, usually about 2 inches. A new build means the full base depth plus any surface layer, entered as separate calculations.
The calculator gave me tons. Where do I order?
Go to the product page that matches the material you selected. Base goes to Class 6 Road Base, drains go to #57 Stone or Drain Rock, and top dressing goes to Driveway Gravel.
How thick should a gravel drive be for normal cars?
A common build is 4 inches or more of compacted Class 6 with a couple of inches of surface gravel on top. On expansive clay, a thicker base helps.
Our lot is expansive clay. What does that change?
Clay moves as it wets and dries, so give it a thicker compacted base and grade the surface to drain. Keep water from pooling at the edges, because wet clay is where ruts start.
Will the gravel sink or settle after I spread it?
Loose rock settles as it packs down, and base settles most. Compacting in lifts takes care of most of that up front, and the 5% option covers the rest.
Related calculators
That tonnage ships free.
Driveway gravel, #57, crusher run: priced by the ton, delivered across Colorado.
