Pea Gravel Calculator
Depth is the whole answer here, and it changes completely with the job: 2 in on a path, 9 in under a swing set. So this pea gravel calculator sets the depth from what you are building, and if you are filling flagstone joints it sizes the gaps rather than the patio.
Your result
What to order
3 tons of pea gravel (2.22 cu yd) for 240 sq ft at 3 in
About $135 at $45 a ton. Add 10% if the ground is uneven, because pea gravel finds every hollow.
- Coverage at this depth
- One ton of pea gravel covers about 80 sq ft at 3 in. A cubic yard weighs 2,700 lb, which is 1.35 tons to the yard.
- It will move
- Pea gravel is rounded, so it rolls. Edging on every side is not optional, and on any slope past about 5% it migrates downhill whatever you do. Plan to rake it back and top it up every couple of years.
- How this is worked out
- 240 sq ft × 3 in ÷ 12 ÷ 27 = 2.22 cu yd × 2,700 lb ÷ 2,000 = 3 tons
How much pea gravel do you need
Multiply the area in square feet by the depth in inches and divide by 324. That gives cubic yards directly, because a cubic yard spread one inch deep covers 324 sq ft. Multiply by 1.35 to get tons.
A 20 by 12 ft patio is 240 sq ft. At 3 in that comes to 2.22 cubic yards, or 3.00 tons, which is 120 of the half cubic foot bags sold at garden centers. Bulk delivery wins comfortably at that size.
Add about 10% on uneven ground. Pea gravel is small and rounded, so it runs into every dip and hollow rather than bridging them the way larger angular stone does. A surface that looks flat before the gravel goes down rarely is.
How deep should pea gravel be
Two inches for a path, three for a patio or dog run, and nine or more under playground equipment. Depth is the single decision that changes the order most, and going deeper is not better on anything you walk on.
| Job | Depth | Cubic yards | Tons | Why |
|---|---|---|---|---|
| Patio or seating | 3" | 0.93 | 1.25 | Deep enough to stay put underfoot without swallowing chair legs |
| Dog run | 3" | 0.93 | 1.25 | Over fabric, so it drains and rinses clean rather than holding odor |
| Path or walkway | 2" | 0.62 | 0.83 | Shallow, with edging both sides or it spreads into the beds |
| Bed mulch | 2" | 0.62 | 0.83 | Over landscape fabric, where it suppresses weeds without breaking down |
| Drainage fill | 6" | 1.85 | 2.50 | Works, but larger washed stone drains better and clogs less |
| Playground surface | 9" | 2.78 | 3.75 | Depth is set by fall height, and 9 in is the usual minimum |
Past three inches a pea gravel surface stops feeling firm and starts feeling like wading, because the stones roll over each other instead of locking. That is the complaint people have about pea gravel patios, and it’s almost always a depth problem rather than a material problem.
The exception is playground surfacing, where depth is doing a completely different job. There the loose, deep layer is the point: it absorbs a fall. Nine inches is a common minimum and taller equipment needs more, so take the figure from the equipment rather than from a landscaping guide.
Pea gravel between flagstone
This is the calculation people get most wrong, and it is wrong in an expensive direction. Filling joints means covering only the gaps, which on a hand-set patio is usually a quarter of the surface.
| Joint style | Share of patio | Area to fill | Tons at 2" |
|---|---|---|---|
| Tight, cut stone | 10% | 24 sq ft | 0.20 |
| Hand-set, regular | 25% | 60 sq ft | 0.50 |
| Informal, wide gaps | 40% | 96 sq ft | 0.80 |
| Whole area (wrong) | 100% | 240 sq ft | 2.00 |
The bottom row is what you order if you treat the patio as open ground: 2.00 tons against the 0.50 tons a normal hand-set patio actually needs. That is four times too much, and pea gravel is not cheap enough to absorb that kind of error.
To find your own share, measure a representative square yard, add up the joint widths across it, and divide by the total. Or just accept 25% for a hand-set patio and 10% for tightly butted cut stone. Order a little over either way, because joints settle and want topping up after the first winter.
Pea gravel for a dog run
Pea gravel is one of the better dog run surfaces, and the reason is drainage. Urine rinses straight through rather than sitting in soil, so the run doesn’t develop the smell that bark and bare earth do.
Lay 3 in over landscape fabric on firm, graded ground. A 240 sq ft run takes about 3.00 tons. The fabric matters more here than anywhere else, because without it the stone works into the mud within a season and you lose both the drainage and the ability to rinse it.
Rinse it through with a hose every few weeks and rake it level. The rounded stone is comfortable on paws, which is the other reason it beats crushed rock: angular edges are hard on pads over time, particularly for dogs that run and turn on the same surface daily.
| Surface | Drains | Holds odor | Comfort on paws |
|---|---|---|---|
| Pea gravel | Yes | No | Good |
| Crushed stone | Yes | No | Hard on pads |
| Bark or mulch | Poorly | Yes | Good |
| Grass | Poorly | Yes | Best |
| Bare soil | No | Yes | Good until wet |
Is pea gravel good for drainage
It drains, but it’s the wrong choice for a drain. Rounded 3/8 in stones nest together tightly, so a cubic yard of pea gravel holds less air than a cubic yard of angular 3/4 in stone, and less air means less water moving through it.
The bigger problem is silt. Small voids block sooner, so a trench filled with pea gravel silts up years before one filled with washed #57 would. If the job is a french drain, footing drain or dry well, use larger washed stone and wrap it in geotextile.
Where pea gravel does earn its place is surface drainage that also has to look good, like a dry creek bed or a gravel bed beside a patio. There it is doing a decorative job with a drainage benefit, rather than being the drain itself.
Pea gravel weight, coverage and cost
A cubic yard weighs about 2,700 lb, which is 1.35 tons, and a ton is roughly 0.74 cubic yards. It’s among the lightest gravels because rounded stones can’t pack as tightly as angular ones.
| Depth | Sq ft per ton | Sq ft per cubic yard | Cost per 100 sq ft |
|---|---|---|---|
| 1" | 240 | 324 | $19 |
| 2" | 120 | 162 | $38 |
| 3" | 80 | 108 | $56 |
| 4" | 60 | 81 | $75 |
| 6" | 40 | 54 | $113 |
Delivered, pea gravel runs around $45 a ton, above crushed stone because it has been washed and screened to a narrow size range. That extra processing is what makes it smooth enough for bare feet, so it’s the whole reason to buy it.
Bagged pea gravel costs several times the bulk rate. The crossover is about half a cubic yard, or 27 bags, so anything larger than a small bed is worth having tipped even after the delivery charge.
Coverage halves each time the depth doubles, so the cost column above climbs faster than it looks. Going from 2 in to 3 in on a patio is not a small adjustment, it is half as much stone again, and on a large area that is the difference between one delivery and two.
Pea gravel questions
How much pea gravel do I need?
Area times depth, divided by 324, gives cubic yards. A 240 sq ft patio at 3 in is 2.22 cubic yards, or about 3.00 tons at 2,700 lb per yard. Filling flagstone joints needs far less, because you only cover the gaps.
Is pea gravel good for drainage?
It works but it is not the best choice. The rounded 3/8 in stones nest together and leave less void space than angular washed stone, and the small size means silt clogs them sooner. For a french drain, 3/4 in washed stone drains better and lasts longer.
How deep should pea gravel be?
3 in for a patio, 2 in for a path, 3 in for a dog run and 9 in under playground equipment. Deeper than 3 in on a walking surface feels like wading; shallower than 2 in and the ground shows through within a season.
How much pea gravel do I need between flagstone?
Only the joints, which is usually 10 to 40% of the patio. On a 240 sq ft patio with 25% joints at 2 in, that is about 0.50 tons against 2.00 tons if you filled the whole area. Measure your joint width before ordering.
Is pea gravel good for a dog run?
Yes, and it is one of the better surfaces. It drains, rinses clean with a hose and does not hold odor the way bark or soil does. Lay 3 in over landscape fabric so it stays separate from the mud, and rinse it through every few weeks.
How many tons of pea gravel in a cubic yard?
1.35 tons, since a cubic yard weighs about 2,700 lb. That makes it one of the lighter gravels, because rounded stones cannot pack as tightly as angular ones. A ton is roughly 0.74 cubic yards.
Does pea gravel need a base underneath?
For a patio or path, yes. Put 3 to 4 in of compacted crushed stone underneath, then the pea gravel on top. Laid straight on soil it sinks in and disappears. For beds and dog runs, landscape fabric over firm ground is enough.
How do you stop pea gravel from spreading?
Edging on every side, and depth no greater than you need. Steel, aluminum or composite edging set proud of the gravel does most of the work. Binding products sold as mulch glue will lock the surface, though they need reapplying and make future planting awkward.