Garden Bed Math

🧭 Garden systemSoil and mulch7 stepsFree working copy

Keep a soil and mulch purchase record, with every label in cubic feet

Quick answer

Write down how many cubic feet each job needs, then turn every label into cubic feet: dry quarts ÷ 25.71, liters ÷ 28.32, cubic yards × 27. Divide each price by its cubic feet and the cheapest way to buy shows up. Under NIST's model rule, mulch is sold by volume and bulk topsoil and gravel by the cubic yard or by weight, so for anything sold by the ton, ask what one yard weighs. One example fall list of four jobs comes to 55.41 cu ft, or 48 bags.

Source: NIST Guide to the SI (SP 811), Appendix B.8 conversion factors, checked October 11, 2026; MSU Extension P2301, mulches, checked October 9, 2026; NIST Handbook 130 (2026), Uniform Regulation for the Method of Sale of Commodities, checked October 11, 2026.

Updated October 12, 2026 Sources checked October 11, 2026 Print the working copy

A shopper walking past pallets of bagged topsoil, potting mix and mulch at a garden center

Decide first

Keep a log, just buy, or ask first?

Do it yourself

Keep the log

Keep it if you're buying for more than one job, or choosing between bags and a bulk load. You need each job's size, a phone calculator and the working copy. Mississippi State Extension says to compare a bulk price with the price of smaller units before you order.

Source: MSU Extension P2301, mulches, checked October 9, 2026.

Skip it

Just buy the bags

Skip the log for one small job with one kind of bag, like topping up a single pot or bed. Use the calculator, round up, and keep the receipt in the shed.

Get help

Ask before a big order

Not sure which material suits the job? Ask your county extension office. Ordering a bulk load? Ask the landscape yard what a cubic yard of that exact material weighs, and what delivery costs, before you settle on a number.

A purchase log filled in for one example fall shopping list Every label turned into cubic feet: 1 cu ft = 25.71 dry qt; 1 cu yd = 27 cu ft (NIST, MSU Extension) Bags rounded up per job. Prices left blank: you write in your own store's. JobNeedLabel unitBoughtCu ftPrice$ / cu ft Bed top-up Raised bed soil 5.33 cu ft 4 x 8 ft, 2 in 1.5 cu ft 4 bags 6 _____ _____ Patio pots Potting mix 1.75 cu ft 45 dry qt 25 qt 2 bags 1.94 _____ _____ Front border Bark mulch 33.33 cu ft 10 x 20 ft, 2 in 2 cu ft 17 bags 34 _____ _____ Path base Gravel 15 cu ft 3 x 20 ft, 3 in 60 lb 25 bags 15 _____ _____ Needed: 55.41 cu ft (2.05 cu yd). Bought: 48 bags, 56.94 cu ft. The gravel alone is 25 bags of 60 lb, 1,500 lb to carry. Store: __________ Date: ________ Left over: ________ Next season, start from the left-over column and last year's cubic feet.
The working copy filled in for one example fall list: four jobs, 48 bags, prices left for you to fill in.

One evening at the table, then one trip to the store

The steps, in order

  1. List every job and its size

    Write one line per job: the bed to top up, the pots, the border, the path. Note length and width in feet and the depth in inches, or the quarts a pot needs.

    Have ready: A tape measure and the working copy.

  2. Get cubic feet for each job

    Cubic feet = square feet × depth in inches ÷ 12. A 4 x 8 ft bed topped up 2 inches needs 32 × 2 ÷ 12 = 5.33 cubic feet. Add up the jobs that use the same material.

    Have ready: Each job's size, and the calculators open on your phone.

    Raised bed soil calculator

  3. Read the unit on every label

    Under NIST's model rule, mulch is sold by volume: cubic feet, cubic yards or liters. Peat is sold by liters or cubic feet, and a label in compressed volume gives the compressed amount. Bulk topsoil, sand and gravel go by the cubic yard or by weight.

    Have ready: Photos of the labels, or the yard's price list.

    Source: NIST Handbook 130 (2026), Uniform Regulation for the Method of Sale of Commodities, checked October 11, 2026.

  4. Turn every label into cubic feet

    One cubic foot is 25.71 dry quarts or 28.32 liters, and a cubic yard is 27 cubic feet. So a 25 quart bag holds 0.97 cubic feet and a 2 cu ft bag holds 51.4 dry quarts.

    Have ready: The conversion line on the working copy.

    Source: NIST Guide to the SI (SP 811), Appendix B.8 conversion factors, checked October 11, 2026; MSU Extension P2301, mulches, checked October 9, 2026.

  5. Work out the price per cubic foot

    For bags: price ÷ the bag's cubic feet. For bulk: (price + delivery) ÷ (yards × 27). Mississippi State Extension says to compare bulk with smaller units before you buy.

    Have ready: Prices from the store and the yard, delivery fee included.

    Mulch calculator

    Source: MSU Extension P2301, mulches, checked October 9, 2026.

  6. Ask the weight for anything sold by the ton

    Stone sold by weight needs one more number: what one cubic yard of it weighs. Then tons × 2,000 ÷ pounds per yard = yards. A 60 lb gravel bag holds about 0.6 cubic feet, so that stone runs about 100 lb per cubic foot.

    Have ready: The yard's weight per cubic yard for that exact stone.

    Gravel and paver base calculator

    Source: Sakrete All-Purpose Gravel data sheet, checked October 6, 2026; NIST Guide to the SI (SP 811), Appendix B.8 conversion factors, checked October 11, 2026.

  7. Log what you bought and what's left

    Write the date, the store, the count, the cubic feet and the price per cubic foot. At the end of the season, note what was left over. Next year's list starts from that line.

    Have ready: The receipt and the working copy.

Free, one page, black and white

Print the working copy

Purchase log: the steps above as a checklist with a date box for each, on one US Letter page.

Open the working copy

If a step gets skipped

What goes wrong

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Comparing bags by sticker price

A quart bag and a cubic foot bag on the same shelf look alike. Price per bag tells you nothing until both are turned into cubic feet, since a 25 quart bag holds just under 1 cubic foot.

Source: NIST Guide to the SI (SP 811), Appendix B.8 conversion factors, checked October 11, 2026.

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Mixing up dry and liquid quarts

Quarts on a soil bag are dry quarts, 1.101 liters each. A milk jug quart is 0.946 liters. Use the liquid quart and a bag looks about 14% smaller than it is.

Source: NIST Guide to the SI (SP 811), Appendix B.8 conversion factors, checked October 11, 2026.

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Reading a compressed bale as loose volume

NIST's model rule says a peat label in compressed volume gives the amount in the compressed state. That number isn't what you'll have once you loosen it, so don't put it in the cubic feet column without a note.

Source: NIST Handbook 130 (2026), Uniform Regulation for the Method of Sale of Commodities, checked October 11, 2026.

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Ordering stone by the ton with no weight

A ton of one stone fills a different space than a ton of another. Without the weight per cubic yard from the yard, tons can't be turned into the cubic feet the job needs.

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Rounding every job up before a bulk order

Rounding each job to whole bags adds a bit every time. For a bulk load, add the cubic feet first and round the total once.

A hand scooping loose potting mix out of a container
What's left in the bag at the end of the season goes in the log too. Next year's order starts from it.
One cubic foot, three ways, and where common bags sit 12 x 12 x 12 in 1 cubic foot = 25.7 dry quarts = 28.3 liters Quarts on soil bags are dry dry quart = 1.101 L liquid quart = 0.946 L A dry quart is 16% bigger 0 Scale in cubic feet, 0 to 2 8 qt 0.31 cu ft 16 qt 0.62 cu ft 25 qt 0.97 cu ft 1 cu ft 25.7 qt 1.5 cu ft 38.6 qt 50 qt 1.94 cu ft 2 cu ft 51.4 qt Factors from NIST Guide to the SI, Appendix B.8 (updated 2025). Checked October 11, 2026.
One cubic foot in dry quarts and liters, with common bag sizes on one scale, from the quarts guide.
Tons and cubic yards are linked by what one yard weighs 1. Read a bag label 60 lb about 0.6 cu ft 60 ÷ 0.6 = 100 lb per cu ft example only 2. One cubic yard 3 x 3 x 3 ft = 27 cu ft 27 x 100 = 2,700 lb 1.35 tons per yard 1 short ton = 2,000 lb 3. The patio base 10 x 12 ft, 4 in deep 40 cu ft = 1.48 yd 40 x 100 = 4,000 lb 2 tons at the example weight Ask the stone yard what one cubic yard of its stone weighs, and use that figure. Bag: Sakrete All-Purpose Gravel bag table. Short ton: NIST Guide to the SI, Appendix B.8. Checked October 11, 2026.
From a gravel bag label to tons per yard, from the tons guide. Ask your yard for the weight of its own stone.

When the steps change

Variants

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Bags only, a small yard

Log by bag: count, bag size in cubic feet, price per cubic foot. The example list needs 4 bags of 1.5 cu ft soil, 2 bags of 25 qt potting mix, 17 bags of 2 cu ft mulch and 25 bags of 60 lb gravel: 48 bags.

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One bulk load

Total the cubic feet for that one material and divide by 27 for cubic yards. The example border's 33.33 cubic feet of mulch is 1.23 cubic yards. Mississippi State Extension gives the 27 and says to compare the bulk price with bags.

Source: MSU Extension P2301, mulches, checked October 9, 2026.

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Pots in quarts, beds in cubic feet

Potting mix is often sold in quarts and bed soil in cubic feet. Divide quarts by 25.71 so both sit in one column. The example pots need 45 dry quarts, which is 1.75 cubic feet.

Source: NIST Guide to the SI (SP 811), Appendix B.8 conversion factors, checked October 11, 2026.

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Stone sold by the ton

NIST's model rule lets bulk aggregate, sand and topsoil be sold by the cubic yard or by weight, and flagstone by weight. Log the tons, the weight per yard the yard gave you, and the cubic feet that works out to.

Source: NIST Handbook 130 (2026), Uniform Regulation for the Method of Sale of Commodities, checked October 11, 2026.

What people learn the second year

Tips and tricks

  • Photograph the label, not the shelf tag. Shelf tags often show only the price per bag. The volume is on the bag itself. One photo of each label gives you everything for the cubic feet column.
  • Ask the yard for the delivery fee first. Bulk prices are per yard, but delivery is often one flat charge. Put it in the bulk line before you compare, or a small load looks cheaper than it is.
  • Keep one column in cubic feet. Whatever the label says, the log's main column stays in cubic feet. With mixed units, a bag that looks cheap can cost more per cubic foot.
  • Write down the left-overs. Half a bag of potting mix in October is part of next spring's order. Note it before the bag gets pushed to the back of the shed.
  • Total the gravel weight before the trip. Bags of stone add up fast. The example path needs 25 bags of 60 lb, 1,500 lb in all. Know that number before you plan the trips. (Sakrete All-Purpose Gravel data sheet)

The one we checked the steps against

Primary source

Handbook 130 (2026), IV. Uniform Regulations, B. Uniform Regulation for the Method of Sale of Commodities, National Institute of Standards and Technology (NIST), Office of Weights and Measures, published December 22, 2025. Checked October 11, 2026.

NIST Handbook 130 (2026) holds the model rule most states base their method-of-sale laws on. It says mulch is sold by volume (cubic yards, cubic feet or liters), peat by liters or cubic feet with compressed volume declared as compressed, and bulk topsoil, sand, gravel and landscape rock by the cubic yard or by weight. Those are the units a purchase log has to turn into cubic feet. It's a model rule, and a state may not have adopted every section.

The arithmetic and the background reading

Tools and guides in this system

Common questions

Questions

How do I compare the price of soil bags of different sizes?

Turn each bag into cubic feet and divide the price by that. Dry quarts ÷ 25.71 gives cubic feet, and liters ÷ 28.32 does too. The bag with the lowest price per cubic foot is the cheaper one, whatever its size.

Source: NIST Guide to the SI (SP 811), Appendix B.8 conversion factors, checked October 11, 2026.

How many cubic feet are in a 40 quart bag?

40 ÷ 25.71 = 1.56 cubic feet. Bags sold as 1.5 cu ft are sometimes also labeled 40 quarts, so the two numbers on one bag can differ a little.

Source: NIST Guide to the SI (SP 811), Appendix B.8 conversion factors, checked October 11, 2026; Miracle-Gro raised bed soil product page, checked October 6, 2026.

Is mulch sold by the cubic yard or by weight?

By volume. NIST's model rule says mulch is sold in cubic yards or cubic feet, or in liters or cubic meters. Bulk topsoil, sand and gravel can be sold by the cubic yard or by weight. States adopt the model rule in whole or in part.

Source: NIST Handbook 130 (2026), Uniform Regulation for the Method of Sale of Commodities, checked October 11, 2026.

When is a bulk load cheaper than bags?

When (bulk price + delivery) ÷ (yards × 27) comes out lower than bag price ÷ bag cubic feet. Mississippi State Extension says to make that comparison before buying in bulk. A flat delivery fee means bags often win on small jobs.

Source: MSU Extension P2301, mulches, checked October 9, 2026.

Why keep a record of what I bought?

Because the same beds and borders come back every year. Last year's cubic feet, price per cubic foot and left-overs turn the next order into a quick check.

The next job on the shelf

More garden systems

Sources

Planning guide, not a guarantee. See every source on the site on the sources page. Spotted an error? Tell us.

Photos: Spencer Plouzek / Unsplash, Alicia Christin Gerald / Unsplash, Kelly Sikkema / Unsplash and 2 more, see photo credits