Gravel Driveway Calculator

Gravel Driveway Calculator: How Much Gravel Do You Need?

A gravel driveway looks simple. You spread some stone and you are done. But the first time you try to order it, the questions pile up. How many tons do I need? Is it sold by the ton or by the cubic yard? How deep should it be? Will it sink into the ground after the first rain?

This gravel driveway calculator answers those questions for you. Enter the length and width of your driveway, pick the soil you have and the vehicles you drive, and the tool suggests a build-up of layers. It then tells you how many tons and cubic yards to order, how many truck loads that is, and what it should cost.

It works for a brand new driveway and for resurfacing an old one that has gone thin. You can mix shapes, so a long straight drive, a flared entrance and a round turnaround can all go into the same estimate. You can use feet and inches or metres and millimetres, and you can type in your own prices. It is free and there is nothing to sign up for.

How to Calculate Gravel for a Driveway

The math has three steps. First, find the volume of the space. Second, add a little extra, because loose gravel packs down once cars drive over it. Third, turn the volume into weight, because most suppliers sell gravel by the ton.

Volume is length times width times depth. If you measure in feet and inches, change the depth to feet first. Divide the answer in cubic feet by 27 and you have cubic yards. Gravel is usually sold in cubic yards or tons, so this is the number your supplier will understand.

Here is a real example. Say your driveway is 50 feet long and 12 feet wide. That is 600 square feet. You want a base of 6 inches and a top layer of 2 inches. The base is 600 x 0.5 = 300 cubic feet, or 11.1 cubic yards. The top layer is 600 x 0.167 = 100 cubic feet, or 3.7 cubic yards.

Now add the extras. Crusher run packs down by about 15 percent, so the base becomes 12.8 cubic yards. Add 5 percent for spills and uneven ground and you reach 13.4 cubic yards. At about 1.5 tons per cubic yard, that is roughly 20 tons. The top layer of #57 stone packs down much less, so it comes to about 5.8 tons. The whole driveway needs close to 26 tons.

Here is a quick rule you can use in your head. Multiply the square feet by the depth in inches, then divide by 230. That gives the tons of gravel before any extra for packing and waste. For 600 square feet at 2 inches, it is 600 x 2 / 230, which is about 5.2 tons. Add 10 to 20 percent and you are close to the 5.8 tons above.

One note on the word ton. In the United States a ton is 2,000 pounds. In most other countries a tonne is 1,000 kilograms, which is a little more. This calculator shows both, so you will not get caught out by the difference.

How to Use This Calculator

Start at the top and work down. If you are unsure about a setting, leave the default. It is a sensible starting point.

• Choose New driveway or Resurface. Pick resurface if you already have gravel and only want to top it up.
• Pick a shape that looks like your driveway, or build your own. You can add up to six sections. Each one can be a rectangle, a tapered strip, a circle or a triangle. A tapered strip is handy for a flared entrance that is wider at the road.
• Tell the calculator about your ground and your traffic. For a new driveway, it suggests how thick each layer should be. You can change any number it gives you.
• Check the stone type for each layer. The weight per cubic yard and the packing allowance change with the type, and the calculator handles that for you.
• Set the crown. This is how much higher the middle of the driveway is than the edges. A small crown helps water run off.
• Enter the price your supplier quoted, per ton or per cubic yard. Turn on delivery, fabric, edging, labor or a compactor rental if you want the full project cost.
• Read the results. Copy the order sheet to send to your supplier, or download the CSV file.

How Deep Should a Gravel Driveway Be?

This is the question we get asked most, and the honest answer is that it depends on your soil and what you drive. A total depth of 6 to 12 inches covers most homes. Firm, dry ground and light cars sit at the low end. Soft clay and heavy vehicles sit at the high end.

A thin driveway fails in a predictable way. The stone gets pushed into the soil, ruts form, and mud works its way up to the surface. Adding more gravel on top of a weak base only hides the problem for a season. It is cheaper to build it properly once.

As a starting point, many people use something like the figures below. They are typical numbers, not a code. Your local supplier or contractor knows the ground in your area, so ask them before you order.

• Firm soil, family cars: about 4 inches of base and 2 inches of top layer, 6 inches in total.
• Average soil, family cars: about 6 inches of base and 2 inches on top, 8 inches in total.
• Average soil, pickups and deliveries: add 4 inches of coarse sub-base under a 4 inch base and a 2 inch top layer, 10 inches in total.
• Soft or wet soil with heavy vehicles: 8 inches of sub-base, 4 inches of base and 2 inches on top, 14 inches in total, plus fabric underneath.

The Layers of a Good Gravel Driveway

The best gravel driveways are not one pile of stone. They are built in layers, and each layer has a job. The calculator follows the same idea, which is why it asks for more than one depth.

The sub-base is the bottom layer. It uses big stone, usually #3 or #4, about 1.5 to 2.5 inches across. The pieces lock together and spread the weight of the car over a wide area. You only need this layer when the ground is soft or the traffic is heavy.

The base is the working layer. Crusher run, also sold as #411 or dense grade aggregate, is a mix of crushed stone and fine dust. When you wet it and compact it, it sets almost like a road. Most of the strength of your driveway comes from here.

The top layer is the part you see. A couple of inches of #57 stone or a finer #8 stone looks clean, drains well and is easy to rake. Because it sits on a firm base, it stays in place far better than a thick layer of loose stone would.

Under all of this, many people lay geotextile fabric. It keeps the stone from mixing with the soil. On clay or soggy ground it is cheap insurance, and it can add years to the life of the driveway.

Which Gravel Is Best for a Driveway?

Not all gravel is the same, and the name on the bag does not always tell you much. In many places the word gravel just means any loose stone. What matters is the size of the pieces and whether they are crushed or rounded.

Crushed stone has sharp edges, so the pieces grip each other. That is what you want under tires. Rounded stone, like pea gravel, rolls around. It looks pretty in a garden path, but it tends to spread out and leave bare patches on a driveway.

For the base, crusher run is the usual favorite because it compacts so well. Recycled concrete is a good budget choice in some areas and packs down just as hard. For the top, #57 is popular because it is a good all-round size. Smaller #8 stone feels smoother to walk on. Quarry fines can be used as a thin dressing, but a thick layer turns to mud when it rains.

The weight of gravel changes with the type. Most driveway stone weighs between 1.35 and 1.5 tons per cubic yard. That is why your tonnage can look different from your cubic yards. The calculator uses a sensible figure for each stone and shows both numbers.

Gravel Driveway Cost: What Will You Really Pay?

Gravel is one of the cheapest driveway surfaces, but the stone is not the only cost. Prices change a lot from place to place. Many suppliers charge somewhere between 25 and 60 dollars per ton for common driveway stone, and delivery is often extra. Treat that as a rough guide only. A call to two or three local suppliers will tell you more than any average.

Delivery is a bigger part of the bill than people expect. A full dump truck carries about 12 tons, so a 26 ton driveway needs around three loads. Many suppliers charge per load, and some have a minimum charge for small orders.

Then come the extras. Fabric, edging, hiring a plate compactor, and paying someone to grade and spread the stone all add up. You can turn each one on in the calculator and see how it changes the total. There is also a contingency box. Five to ten percent is a sensible cushion for a job that has surprises in it.

The calculator also shows a yearly top-up estimate and a ten year cost. Gravel thins out as cars push it aside and rain washes some away. Many owners add an inch or two every couple of years. Looking at this number early gives you a fairer comparison with a paved driveway.

New Driveway or Resurfacing?

If you already have a gravel driveway, you may not need to start from scratch. A thin, patchy surface on a solid base can often be fixed with a fresh top layer. Loosen the surface with a rake, fill the low spots and add about 1 to 2 inches of new stone.

Use the Resurface option for this. Enter the depth you think is left and the depth you want, and the calculator works out the difference. It also lets you add a bit extra for ruts and low spots, which is where most of the new stone ends up.

If your driveway has deep ruts, soft spots that hold water, or mud coming through the stone, a top-up will not last. The base has failed. In that case it is better to dig out the weak areas and rebuild with proper layers.

Crown, Drainage and Edges

Water is what kills a gravel driveway. If rain sits on the surface or runs down the middle, it carries stone away and softens the base. The fix is a gentle crown, where the middle is higher than the edges so water runs off to both sides.

A slope of about a quarter inch per foot works well. On a 12 foot wide driveway, the middle should be about 1.5 inches higher than the edges. Because the crown is shaped like a roof, the extra stone you need is about half of that height, spread across the whole surface. The calculator adds this to your top layer for you.

Also think about where the water goes once it leaves the driveway. A ditch, a swale or a gentle slope away from the house keeps it from pooling. Edging, such as timber, steel or stone, helps hold the gravel in and keeps the edges tidy. It also keeps the grass from creeping in.

Mistakes to Avoid When Ordering Gravel

Most problems with gravel driveways come from a handful of simple mistakes. Here are the ones we see again and again.

• Forgetting that gravel packs down. If you order exactly the volume you measured, you will be short.
• Skipping the base and putting only pea gravel or #57 stone on bare ground. It sinks and the driveway turns to mud.
• Comparing quotes in different units. One supplier quotes per ton and another per cubic yard. Convert both to the same unit first.
• Laying everything in one thick pass. Spread and compact each layer separately so the stone locks together.
• Ignoring drainage. A perfect driveway with no way for water to leave will still wash out.
• Measuring only the straight part. Turnarounds, flared entrances and parking pads all take stone too.

Looking After Your Gravel Driveway

A little care every year keeps a gravel driveway in good shape for a long time. Rake the surface now and then to fill ruts and spread stone back from the edges. Fill low spots before they hold water. If you plow snow, raise the blade slightly so it does not scrape up your top layer.

Keep an eye on weeds. Fabric under the stone helps, and so does pulling them while they are small. Every few years, add a thin top-up of the same stone you used before. A new layer of an inch or two usually brings the surface back to life.

Before You Place Your Order

Take a few minutes to check your numbers. Measure the driveway twice. Confirm with the supplier how much each cubic yard weighs, and whether the price includes delivery. Make sure the truck can reach the spot without damaging a gate, a power line or soft ground. Decide where the first load will be dumped, so you are not moving stone by wheelbarrow all day.

This calculator gives an estimate, not a quote. Stone weight, local prices and ground conditions all vary, so check the final amount with your supplier or a local contractor before you buy.