Mulch Calculator

How much mulch do I need?

Mulch is sold by the cubic yard in bulk and by the cubic foot in bags, but you measure your yard in square feet. The whole job is converting between the two, and there is one number worth memorising: one cubic yard of mulch covers 324 square feet at one inch deep. Everything else follows from dividing that by your depth.

At the three inch depth most beds want, a yard covers 108 square feet. So a bed that measures 20 feet by 25 feet, which is 500 square feet, needs a bit under five cubic yards. The calculator above runs that math for any shape, but the table is worth a look because it tells you how sensitive the answer is to depth.

Going from two inches to four inches doubles your order. That single decision moves the cost of a mid sized job by a few hundred dollars, so it is worth being deliberate about it rather than defaulting to whatever looks right.

How deep should mulch actually go?

Two to three inches is the working range for most beds. Three inches suppresses weeds properly and holds moisture through a hot week. Below two inches you get colour and not much else, because light still reaches the soil and weed seed germinates anyway.

Four inches is only worth it on brand new beds with bare soil and a real weed problem, and even then you want to keep it well clear of trunks and stems. Piling mulch against a tree trunk holds moisture on the bark and invites rot, which is the mistake you see in half the parking lot islands in America. Pull it back two or three inches from anything woody.

If you are topping up an existing bed rather than starting fresh, measure what is already there first. Most people only need an inch to bring the colour back, not a full three. Old mulch does not disappear, it composts down into the soil surface, and stacking new mulch on top year after year eventually smothers shallow roots.

Mulch weight by type, and why it matters

This is the part generic calculators skip, and it is the part that costs people money. Mulch is not one material. A cubic yard of pine bark nuggets and a cubic yard of rubber mulch occupy the same space in the bed and weigh completely different amounts, which matters the moment your supplier prices by the ton or your truck has a payload limit.

Two practical consequences. First, if you are hauling it yourself, five yards of hardwood is roughly two tons and that is past the payload of every half ton pickup on the road. Second, rubber mulch is usually bagged at 0.8 cubic feet where wood mulch comes in 2 cubic foot bags. People compare the shelf price bag to bag, buy rubber thinking it is similar money, and end up paying three times as much per cubic foot of actual coverage.

Bags or bulk delivery?

There are 13.5 standard 2 cubic foot bags in a cubic yard. At $4.50 a bag that is $60.75 per yard in bagged mulch, against maybe $38 per yard in bulk plus a flat delivery fee of $60 to $100 depending on how far out you are.

So the question is not which is cheaper per yard, bulk always wins on that. The question is whether you are buying enough yards for the savings to cover the delivery fee. With the numbers above you are saving about $23 per yard by going bulk, so a $75 delivery pays for itself at roughly 3.3 yards. Under three yards, bags usually win and you avoid a pile in the driveway. Over four, bulk is clearly ahead and the gap widens fast.

The calculator runs this with your actual local prices, which is the part that matters, because bulk rates swing a lot by region and a delivery fee in a rural county looks nothing like one in a dense suburb.

Two things the pure math misses. Bags are easier if you cannot get a truck near the beds or you are working across several weekends, since an opened pile of bulk mulch starts breaking down and growing fungus. And plenty of yards will waive the delivery fee entirely over a certain order size, usually five or six yards, so it is worth asking before you assume.

Measuring a bed that is not a rectangle

Almost no real planting bed is a clean rectangle, which is why so many people end up guessing. The reliable approach is to stop trying to find one formula and instead break the bed into pieces you can measure, then add them up. The calculator above lets you add as many sections as you need.

• Long curved border. Treat it as a rectangle. Measure the length along the curve with a tape laid on the ground, then measure the width at three or four points and average them. Curves in and out cancel each other out well enough at mulch depth.
• Island bed. Usually a circle or an oval. For a circle, measure straight across at the widest point and use that as the diameter. For an oval, measure the long axis and short axis, then treat it as a rectangle and take off about 20 percent.
• Ring around a tree. Use the ring option. Measure the full diameter of the mulched circle, then the diameter of the bare area you are leaving around the trunk. The calculator subtracts the middle so you are not buying mulch for ground you are not covering.
• Corner or triangle. Measure the two straight legs against the fence or path and use the triangle option.

Round up to the nearest half yard when you order bulk. Mulch settles, you will find a spot you forgot, and nobody has ever regretted having a wheelbarrow too much. Coming up half a yard short means either a second delivery fee or a bed that looks patchy all season.

Mistakes that cost money

Ordering by the ton without checking density. If your supplier quotes by the ton and you calculated in yards, you need the right weight per yard for the specific mulch you are buying. Using a generic 800 pounds for lava light pine bark means ordering nearly double what you need.

Forgetting the bed is already partly full. Existing mulch counts. Measure the gap between the current surface and where you want to be, not the full three inches.

Buying dyed mulch for a vegetable garden. Dyed mulch is usually ground construction and pallet wood. The dye itself is generally iron oxide or carbon and not the concern, the source wood is. Use natural bark or straw around anything you plan to eat.

Mulching over a weed problem instead of under it. Three inches of mulch stops seed germinating. It does not stop established perennial weeds, and bindweed in particular will come straight through. Clear those first or you are burying a problem you will dig out again in July.

Common questions

How many bags of mulch are in a cubic yard?

It depends on the bag size. A cubic yard is 27 cubic feet, so you get 13.5 bags at the standard 2 cubic foot size, 18 bags at 1.5 cubic feet, or 9 bags at 3 cubic feet. Rubber mulch is usually bagged at 0.8 cubic feet, which works out to about 34 bags per yard.

How much does a yard of mulch cover?

324 square feet at 1 inch deep, 162 square feet at 2 inches, 108 square feet at 3 inches and 81 square feet at 4 inches. Three inches is the usual target for established beds.

How much does a cubic yard of mulch weigh?

Anywhere from 400 to 1,400 pounds depending on the material and how wet it is. Pine bark runs 400 to 600 pounds, shredded hardwood 700 to 1,000, and rubber mulch 1,100 to 1,400. A pile that has been rained on can weigh 20 to 30 percent more than the same mulch dry.

Will 5 cubic yards of mulch fit in a pickup truck?

No. A full size pickup bed holds roughly 2 to 2.5 cubic yards level with the rails, and weight becomes the limit before volume does. Five yards of hardwood mulch is around 2 tons, which is well over the payload of any half ton truck. Most people either take three trips or pay the delivery fee.

Should I remove old mulch before adding new?

Usually not. Old mulch breaks down into the soil and adds organic matter, so raking it level and topping up an inch is normally the better move. Remove it if it has gone matted and water is running off rather than soaking in, or if you have had a fungal problem you do not want to carry over.

How do I calculate mulch for an irregular shaped bed?

Break it into simple shapes, measure each one and add the areas together. A long curved border measures as a rectangle using the length along the curve and the average width. Island beds are usually close enough to a circle or oval. The calculator on this page lets you add as many sections as the bed needs.

How is this different from a big box store mulch calculator?

The math is the same square footage and depth conversion any calculator runs. The difference here is the bag versus bulk comparison using your actual local prices, the multi-section tool for beds that are not one rectangle, and results broken out by the actual density of the mulch type you picked rather than one generic number applied to everything from pine bark to rubber.

These figures are planning estimates. Bulk material weight shifts with moisture and screen size, and suppliers round differently, so confirm the final quantity with your yard before you order.