Michigan Gravel Calculator: Plan in Winter, Build After the Thaw
Enter your project dimensions
Most Michigan gravel jobs get planned in January, when nobody's compacting 21AA over frozen ground anyway. That makes winter a good time to sit down with this gravel calculator, a tape measure and a sketch, and have the order ready when frost comes out.
Here's how one plan comes together, start to finish, before you touch the tool yourself.
Worked example: a 24 x 24 ft garage pad
A detached two-car garage needs a base under it. Six inches of 21AA limestone, compacted.
In the calculator: rectangle, length 24, width 24, depth 6, material "Crusher run / road base", 5% box ticked.
By hand:
- Area: 24 x 24 = 576 sq ft
- Volume: 576 x 6 ÷ 12 = 288 cu ft
- Cubic yards: 288 ÷ 27 = 10.67
- Tons: 10.67 x 1.50 = 16.0
- With 5% for compaction and spillage: 11.2 cu yd, 16.8 tons
So the order is about 17 tons of 21AA. That's the figure to take to the product page.
On the lake plain in the southeast, where flat clay holds water through the thaw, don't trim that depth. On the sandy west side, the ground drains faster, but the pad still has to carry the load.
Entering a cottage pad or drive
Pick one of three shapes. Rectangle is for pads, drives and paths. Circle takes one diameter, handy for a fire ring or turnaround. Multiple areas totals up to five pieces, so a garage pad plus its apron can go in one run.
Measurements go in feet; depth goes in inches, between 0.25 and 24. Choose the material next, then decide on the 5% extra. The answer appears as cubic yards, tons and cubic feet. If you'd rather keep it, Email my quote sends the estimate over.
How 21AA and pea stone convert to tons
Cubic feet is length x width x depth, once depth is in feet (inches ÷ 12). Cubic yards is that ÷ 27. Tons is yards x the material's weight per yard, which the calculator takes from this list:
| Material in the dropdown | Approx. weight | Tons per yard |
|---|---|---|
| Crusher run / road base (use for 21AA) | 3,000 lb | 1.50 |
| Crushed stone (#57, 3/4") | 2,800 lb | 1.40 |
| Pea gravel (3/8") | 2,800 lb | 1.40 |
| Driveway / walkway gravel | 2,800 lb | 1.40 |
| River rock (1-3") | 2,700 lb | 1.35 |
Two quick examples to see it at work. Both use materials at 1.40 tons per yard, so only the volume changes the answer.
Drip strip under the eaves. 44 ft of house, a 2 ft strip, 3 inches of pea stone. 44 x 2 = 88 sq ft; 88 x 3 ÷ 12 = 22 cu ft; 22 ÷ 27 = 0.815 cu yd; 0.815 x 1.40 = 1.14 tons. It catches roof runoff where downspouts aren't worth adding.
Backfill behind a block wall. A wall 28 ft long, stone zone 18 inches thick and 2 ft high. Enter length 28, width 1.5 (the thickness), depth 24 (the height, which just fits the tool's limit). 28 x 1.5 = 42 sq ft; 42 x 24 ÷ 12 = 84 cu ft; 84 ÷ 27 = 3.11 cu yd; 84 ÷ 27 x 1.40 = 4.36 tons of #57 stone.
Extra 21AA for a plate compactor
The 5% option is there for stone that packs down. Use it on 21AA and anything else you'll run a plate compactor over. Loose decorative stone doesn't need it.
Measure depth in more than one spot. Yards and old drives settle unevenly, and one reading can be off by an inch, which on a 576 sq ft pad is roughly 1.8 cubic yards.
Timing is the other half. Base, driveway and paver work runs from the spring thaw into late fall. Frost laws limit heavy trucks on many county roads while the ground thaws, and up north and in the Upper Peninsula those limits can stay later. Pick a delivery date with that in mind.
Picking the right material
- 21AA limestone: the standard Michigan driveway and pad base, a crushed limestone with fines named for the MDOT 21AA class. That class name is how the material is specified here, not a certification.
- 22A road gravel: a separate MDOT class, used on unpaved drives and private roads. It's not a drainage stone.
- Pea stone: rounded, good for paths, play areas and drip strips. It rolls under tires, so keep it off drives.
- #57 and 3/4 inch crushed stone: angular, clean, and the choice for drainage and backfill.
- Drain rock: French drains and downspout runs, especially in slow-draining southeast clay.
Frost reaches 42 inches under the state residential code, and local building officials can ask for more where winters are colder. Gravel sits well above that, which is exactly why a thin layer heaves. The fix isn't more depth than the tool allows; it's a compacted base of the right thickness on ground that drains, laid after the thaw has finished and the soil has firmed up.
When the thaw comes
Have your tons ready, then open the product page, choose the quantity and a date after frost is out, and check out. Delivery is arranged at checkout by ZIP code; leave a clear, firm spot for the truck to dump. Michigan Rock Supply can be reached by call or text through the contact page if you'd like to talk through 21AA versus 22A first.
Common questions
The calculator says 16.8 tons. Do I order 16 or 17?
Order 17. Being a little over leaves stone for patching after next spring's thaw; being short leaves a thin corner you'll notice.
Does it matter if I pick pea stone or crushed stone in the dropdown?
Not for the tons, since both are figured at about 2,800 lb per yard. It matters for the job: pea stone is round and shifts, crushed stone locks together.
How do I figure stone for a handful of ruts and holes in the two-track?
Measure each hole's length, width and depth and enter them as separate areas, up to five per run. Add runs together if there are more.
My flower bed has a wavy border. How do I get a usable number?
Box it in with the smallest rectangle that fits, then estimate what share is actually bed. Or split it into two or three rectangles and let the multiple-areas option add them.
How many trips is that in my trailer or loader?
Divide the calculator's cubic yards by your trailer or bucket capacity in yards. Then check the ton figure against the trailer's rated load, since stone is heavy for its size.
Related calculators
That tonnage ships free.
Driveway gravel, #57, crusher run: priced by the ton, delivered across Michigan.
