Shed Base Concrete Mix Calculator: Sand & Ballast

Answer first: a 10 ft x 12 ft shed base at 4 inches needs about 1.63 yd3 of concrete with 10% waste, or about 1.25 m3 and 74 common 80-lb bags. For a 10 ft x 16 ft shed base at 4 inches, use about 2.17 yd3 with 10% waste, or about 1.66 m3 and 98 common 80-lb bags.

If you are planning a raw-material mix instead of bagged concrete, calculate the slab volume first. Separate-ingredient quantities require specified cement, sand and coarse-aggregate proportions and an applicable dry-volume factor. All-in ballast needs its own batching method. Neither a default ratio nor a factor selected in a calculator establishes concrete strength.

The comparison below uses one 10% allowance. The raw-material rows illustrate a hypothetical 1:2:3 separate-ingredient ratio and 1.54 dry-volume factor; this is not a mix design or an approved purchasing recipe.

Buy/check row	10x12 x 4 in shed base	10x16 x 4 in shed base
Concrete volume after 10% waste	1.63 yd3 / 1.25 m3	2.17 yd3 / 1.66 m3
Common 80-lb bagged mix	74 bags	98 bags
Common 60-lb bagged mix	98 bags	131 bags
Cement in a rough 1:2:3 raw mix	about 0.42 yd3 dry volume	about 0.56 yd3 dry volume
Sand in a rough 1:2:3 raw mix	about 0.84 yd3	about 1.11 yd3
Separate coarse aggregate in the example	about 1.25 yd3	about 1.67 yd3
Cement bag purchase	Obtain bag bulk volume or a specified weight-based batching schedule	Do not convert dry cement volume to mass without applicable density data

For a 10x16 shed base, confirm whether the shed maker means the exact floor footprint, the outside skid/base dimension, or a concrete pad that extends beyond the shed. A 10x16 formed pad and an 11x17 support pad are different concrete orders.

Calculate the required concrete in yd3 or m3 first, then compare bagged concrete, a specified site mix and ready-mix. This guide's volume examples are rectangular slabs; sheds can have other foundations. Do not substitute a mortar bed or assume a slab is required without checking the design.

Use the Concrete Shed Base Calculator for finished pad size, thickness, waste, and bag count. Use the Concrete Mix Ratio Calculator when you want a separate-ingredient quantity estimate with independently specified inputs. Its cement-bag size is volumetric, not an automatic kg-to-volume conversion. Compare the buying path in the Ready-Mix vs Bags Calculator before ordering.

Shed base mix answer in one screen

Use this quick table before buying materials:

Shed base size	Concrete with 10% waste	80-lb bags	Site-mix decision
6 ft x 8 ft x 4 in	0.65 yd3	30	Bags are usually simpler if access is easy.
8 ft x 10 ft x 4 in	1.09 yd3	49	Compare bag labor with small-load delivery.
10 ft x 12 ft x 4 in	1.63 yd3	74	Ready-mix or a planned crew becomes worth checking.
10 ft x 16 ft x 4 in	2.17 yd3	98	Almost 8,000 lb of dry mix; price ready-mix and access.
12 ft x 16 ft x 4 in	2.61 yd3	118	Usually a ready-mix or contractor-scope job.

The bag tables assume 0.60 ft3 per 80-lb bag and 0.45 ft3 per 60-lb bag; use the actual product yield. The decision is not only the number of bags. For a 10x12 pad, 74 80-lb bags are about 5,920 lb of dry mix before water. For a 10x16 pad, 98 80-lb bags are about 7,840 lb of dry mix. That is a staging, lifting, mixing, and finish-timing problem as much as a calculator result.

Metric and Philippines supplier note

For metric quotes, keep the order in m3 and ask the supplier which cement bag size, sand unit, and gravel or ballast unit they actually sell. A rough 10x12 x 4 in shed base is about 1.25 m3 after waste. A rough 10x16 x 4 in shed base is about 1.66 m3 after waste.

Supplier quote item	What to verify before comparing prices
40 kg or 50 kg cement bags	Bag counts change with cement density and the supplier's batching practice.
Sand and gravel by m3	Confirm loose volume, delivered volume, moisture, and whether gravel is separated from sand.
Ballast by bag or m3	Confirm grading and whether it is suitable for the intended concrete mix.
Ready-mix by m3	Ask for billable m3, VAT or tax, delivery, waiting time, chute reach, and rain-delay terms.
Site-mix labor	Confirm who owns batching, water control, placement speed, finishing, curing, and cleanup.

Keep quotes in the same volume and currency units. Ask which taxes and delivery charges are included; do not import a price or tax assumption from another market. Confirm whether aggregate is separate sand and gravel or a blended product before applying a material list.

Formula for a shed base concrete mix calculator

Start with concrete volume:

area ft2 = length ft x width ft
cubic feet =
  area ft2 x thickness in / 12

cubic yards =
  cubic feet / 27

factor = 1 + waste percent/100
order volume = cubic yards x factor

For a 10 ft x 12 ft base at 4 inches:

10 x 12 x 4 / 12 = 40 ft3
40 / 27 = 1.48 yd3 before waste
40 x 1.10 = 44 ft3 with waste
44 / 27 = 1.629629... yd3

For bagged concrete:

80-lb bags =
  order cubic feet / 0.60 ft3 per bag

For a 10x12 x 4 in shed base:

40 ft3 x 1.10 = 44 ft3
44 / 0.60 = 73.333333... bags
round up to 74 80-lb bags

For a 10x16 x 4 in shed base:

10 x 16 x 4 / 12 = 53.333333... ft3
order ft3 = (10 x 16 x 4 / 12) x 1.10
order ft3 = 58.666666...
order yd3 = order ft3 / 27
order yd3 = 2.172839...
bags = order ft3 / 0.60 = 97.777777...
round up to 98 80-lb bags

Retain unrounded geometry in the calculation and round only the displayed volume and final whole-bag count. Do not multiply rounded displayed yards back into cubic feet. The allowance is already applied once.

Always confirm the yield printed on the bag you buy. Fast-setting, high-strength, or regional bags may not match common planning yields.

Raw cement, sand, and ballast estimate

If you are not buying premixed bags, do not start with "how many cement bags?" Start with the finished concrete volume and the applicable specified batching method. The dry-volume factor depends on materials and assumptions; 1.54 is only the hypothetical input used below, not a universal or conservative guarantee.

For a rough 1:2:3 planning mix:

dry ingredient volume =
  wet concrete volume x 1.54

total ratio parts =
  1 cement + 2 sand + 3 stone = 6

cement volume =
  dry ingredient volume x 1 / 6

sand volume =
  dry ingredient volume x 2 / 6

separate coarse aggregate volume =
  dry ingredient volume x 3 / 6

For the 10x12 x 4 in example:

Step	Result
Wet concrete volume with waste	1.63 yd3
Dry ingredient volume at 1.54 factor	2.51 yd3
Cement, 1 part	0.42 yd3
Sand, 2 parts	0.84 yd3
Separate coarse aggregate, 3 parts	1.25 yd3

For a 10x16 x 4 in example:

Step	Result
Wet concrete volume with waste	2.17 yd3
Dry ingredient volume at 1.54 factor	3.34 yd3
Cement, 1 part	0.56 yd3
Sand, 2 parts	1.11 yd3
Separate coarse aggregate, 3 parts	1.67 yd3

That raw-material table is a planning check, not a certified mix design. A real shed slab may need a specified compressive strength, reinforcement, air entrainment, water-cement control, vapor barrier, or local frost requirement.

Do not substitute all-in ballast for the stone row

Tarmac's ballast already contains sand and gravel. Adding the separate sand row to that blend changes the proportions and can count sand twice. Check the exact product and its specified batching instructions. The separate-ingredient calculator is not an automatic cement-to-ballast calculator. Premixed concrete likewise already contains its dry ingredients; follow its label instead of adding raw-material rows to it.

Bagged concrete vs site mix vs ready-mix

Buying path	Best when	Main risk
Bagged concrete	Small pads, hard truck access, simple DIY work.	Many batches, heavy lifting, and inconsistent finishing pace.
Site-mixed cement/sand/ballast	Experienced crew, controlled batching, local materials on site.	Moisture, ratio mistakes, strength uncertainty, and slower placing.
Ready-mix	Larger shed bases, continuous finish work, or tight timing.	Minimum billable yards, short-load fees, access, wait time, and delivery windows.
Contractor quote	Base prep, forms, finish, anchors, drainage, or code issues are unclear.	Quote may hide gravel, reinforcement, cleanup, warranty, or access charges.

For a single 6x8 pad, bags can be reasonable. For a 10x12 or 12x16 pad, the question usually becomes: can the crew place the concrete fast enough and finish it cleanly before the mix gets away from them?

If the answer is unclear, run the yardage in the Concrete Quote Reviewer and ask suppliers for minimum billable yards, short-load fees, chute reach, wait-time policy, and a written delivered total.

Rain, access, and quote checks before buying

The material number is not enough for a shed base that has to be poured, finished, and protected on the same day.

Jobsite check	Why it changes the buying path	What to ask before ordering
Rain or wet-season timing	Wet forms, soft base, and a delayed finish can ruin a "cheap" material plan.	Who decides delay, cancellation, cover, and curing protection?
Gravel base and compaction	A weak base can crack even if the concrete volume is correct.	Is excavation, granular base, compaction, and drainage included?
Truck access or wheelbarrow route	A small slab can become expensive if the truck cannot reach the forms.	What is chute reach, route distance, buggy/pump need, and wait-time policy?
Bag staging and mixer pace	74-98 bags is a lot of lifting and batch timing.	How many people, mixers, and batches can be placed before finishing starts?
Finish and anchor scope	Shed anchors, slope, broom finish, and curing are often missing from material quotes.	Are finish, anchors, joints, curing, cleanup, and warranty written into scope?

For rain-prone markets, including many Philippines job schedules, do not only ask for a cheaper m3 or cement-bag number. Ask who owns the weather decision before the truck is dispatched or before raw materials are opened on site.

What to include in the shed base scope

The concrete mix number is only one line in the job. Before approving a supplier order or contractor quote, check these rows:

Scope row	Why it changes the result
Finished pad size	The concrete follows the formed pad, not only the shed catalog footprint.
Thickness	A 5 in pad uses 25% more concrete than a 4 in pad.
Gravel base	Excavation, gravel depth, compaction, and drainage are separate from concrete volume.
Reinforcement or anchors	Mesh, rebar, thickened edges, and anchor bolts can change labor and quote scope.
Access route	Chute reach, wheelbarrow distance, buggy, or pump needs can decide ready-mix feasibility.
Weather timing	Rain, heat, cold, and finishing windows can matter more than bag price.
Cleanup and warranty	A low quote may exclude spoil removal, form stripping, curing, or crack language.

For gravel below the slab, use the Shed Base Gravel Depth Guide. For bag yield assumptions, use the Concrete Bag Yield Chart. For supplier minimums, review Concrete Short-Load Fee and Minimum Concrete Delivery Order.

Copy-paste supplier questions

Send this when you are comparing bags, site-mix, and ready-mix:

Shed slab: [length] x [width]
Specified thickness: [value, unit]
Order volume: [yd3 or m3]
Allowance already applied: [percent]

Please confirm:
- specified mix and quantity
- physical and billable volume
- included delivery and tax
- conditional fees and waiting time
- access and chute reach
- rain and cancellation terms
- or specified site-mix quantities
- cement product and bag size
- separate aggregate or all-in blend
- water and batching responsibility
- prep, forms, reinforcement, anchors
- finish, cure, cleanup and warranty
- each inclusion and exclusion

If a quote only says "sand and cement" or gives a low material total without aggregate, base prep, access, and finishing language, treat it as incomplete until the supplier or contractor rewrites the scope.

Sources and checks

This page uses common planning conversions. It does not replace bag labels, supplier mix tickets, local code, or professional design.

Check	Source	How it is used
Bag yield and slab volume workflow	QUIKRETE calculator and Sakrete concrete calculators	Cross-checks the bag-count workflow before converting a shed pad into bags.
Ready-mix ordering context	NRMCA concrete in practice resources	Keeps the page focused on ordering, delivery, placement, and quote risk.
Raw-material planning boundary	Portland Cement Association concrete basics	Reinforces that concrete performance depends on materials, water, proportioning, curing, and placement.

Concrete Estimator Hub is independent and is not affiliated with these manufacturers, associations, suppliers, or contractors.

FAQ

What is the best concrete mix for a shed base?

Use the mix specified for your slab's strength, exposure and construction requirements. Bagged concrete, ready-mix and a controlled site mix are supply options, not interchangeable design approvals. A nominal ratio alone does not establish strength or the correct water content.

Can I use sand and cement only for a shed base?

Usually no. Sand and cement alone is closer to mortar than normal concrete. For a concrete slab, confirm the specified concrete mix, including fine and coarse aggregate and water control. All-in ballast is a blend, not a substitute for a separate coarse-aggregate row while retaining all the added sand.

How much concrete do I need for a 10x12 shed base?

At 4 inches thick, a 10x12 shed base needs about 1.48 yd3 before waste or 1.63 yd3 with 10% waste. That is about 74 common 80-lb bags.

Is 4 inches thick enough for a shed base?

Four inches is a common planning thickness for simple light-duty pads, but the right thickness depends on shed size, loads, soil, drainage, frost depth, reinforcement, and local requirements. Confirm code-sensitive work locally.

When should I use ready-mix instead of bags?

Price ready-mix when the shed base reaches pallet-scale bag counts, when you need one continuous pour, when access is reasonable, or when finish timing is too risky for hand mixing. Ask for delivered total, minimum billable yards, short-load fee, wait-time rules, and chute or access limits. If the question is specifically whether delivered concrete is cleaner than a long bag day, use Ready-Mix Concrete for Shed Base as the next step.

Next step

Run the pad size in the Concrete Shed Base Calculator. Then use the Concrete Mix Ratio Calculator for cement, sand, aggregate, and dry-volume assumptions, and use the Ready-Mix vs Bags Calculator before deciding whether to haul bags or call a supplier. If the buying question is still just "bag day or truck day", open Ready-Mix Concrete for Shed Base before you order.