Shed Foundation Concrete Estimator
Shed Base Calculator: 8x10 49 Bags, 10x12 74 Bags
Answer first: an 8x10 shed base at 4 in thick needs about 1.09 yd3 or 49 80-lb bags; a 10x12 needs 1.63 yd3 or 74 bags. Then check whether bags, ready-mix, or a contractor quote is the safer buying path.
Updated September 10, 2026
Finished base 8x10
1.09 yd3
49 80-lb bags
Compare bags with short-load ready-mix
Finished base 10x12
1.63 yd3
74 80-lb bags
Compare bags with short-load ready-mix
Finished base 12x16
2.61 yd3
118 80-lb bags
Compare bags with short-load ready-mix
Enter Shed Base Size
Save this estimate or download a PDF report
The PDF report uses the current calculated result. Save the estimate first when you want to reuse the inputs later.
Results
Live estimateBase prep + mix decision
Check gravel, self-mix, bags, and quote lines before ordering
Concrete uses one entered allowance. Gravel is in-place geometry at an assumed 4 in depth, not a loose order or tons. Nominal separate cement:sand:coarse aggregate volumes assume 1:2:3 and a 1.54 dry-volume factor; not a strength-approved mix or cement bag order.
Keep granular base removal and compaction cost separate from the concrete order before approving a shed-pad quote.
0.99 yd3 in place
3920 lb dry mix
0.28 yd3, not a bag order
| Decision row | Planning value | What to verify |
|---|---|---|
| Concrete pad | 1.09 yd3 with waste | Use the finished formed pad size, not only the shed catalog footprint. |
| Assumed 4 in gravel base | 0.99 yd3 in place | Not a specified depth or loose order. Confirm the designed footprint, material compaction relationship and density before ordering by volume or mass. |
| Bagged mix load | 49 80-lb bags / 3920 lb dry mix | Pallet-scale lifting and finish timing need a store delivery or truck quote. |
| 1:2:3 site-mix screen | 0.28 yd3 cement + 0.56 yd3 sand + 0.84 yd3 coarse aggregate | Assumed 1:2:3 volumes and 1.54 dry factor only. Cement bags require applicable bulk density and bag mass. Separate coarse aggregate is not all-in ballast; confirm an approved mix. |
| Quote scope | Bag delivery, mini-mix, or short-load comparison | Ask for base prep, concrete, access, finish, anchors, cleanup, and exclusions in writing. |
Quick answer
An 8 ft x 10 ft shed base at 4 in thick with 10% waste needs about 1.09 yd3, or 49 80 lb bags at 0.60 ft3 yield. A 10 ft x 12 ft base is about 1.63 yd3 and 74 80 lb bags; a 12 ft x 16 ft base is about 2.61 yd3 and 118 80 lb bags.
Shed base install scope
Turn shed pad bags into a site-ready plan
Shed calculators usually stop at pad size and bag count. This layer keeps the concrete math, then checks the details that decide whether the shed base will actually work: manufacturer base size, overhang, gravel base, drainage, ramp landing, anchors, backyard access, and bag staging.
80 sq ft
Bag labor and mixer rental check
72/100
| Scope check | Why it matters |
|---|---|
| Finished pad dimensions include shed manufacturer base size, doorway clearance, and overhang. | A shed model footprint is not always the finished concrete pad size. |
| Excavation, gravel base depth, compaction, drainage, and moisture control are specified. | Shed base failures often start with water, soft soil, or missing compaction. |
| Ramp landing, mower entry, anchor layout, reinforcement, and edge forms are separated. | Doorway and mower access can add a separate pour section. |
| Backyard access, bag staging, mixer location, wheelbarrow route, and washout are planned. | Small pads can still fail on access, mixing pace, and staging. |
Turn the shed-base result into a buying path
The calculator answer should become a store order, ready-mix quote, or installed-scope review before money changes hands.
You are buying bags from a store
Turns bag count into pallets, loose bags, mixer rental, delivery, and unloading.
Build shopping listYou need base depth or drainage clarity
Keeps excavation, compacted depth, geotextile, and drainage separate from concrete volume.
Check gravel base depthYou need to compare crew, access and delivery options
Checks ready-mix minimums, short-load fees, delivery, labor, and finish timing.
Compare bags vs truckYou want a ready-mix-first shed base check
Normalizes minimum load, access, and quote scope before you order.
Read ready-mix shed guideYou have an installed shed-pad quote
Separates concrete volume from gravel, forms, anchors, drainage, access, cleanup, and labor.
Review shed pad quoteShed base formula
Pad area
Area = finished pad length x finished pad widthArea = 10 x 8 = 80.00 sq ftConcrete volume
Volume = pad length x pad width x thicknessVolume = 10 x 8 x 0.333Waste and bags
Final volume = 26.6667 x (1 + 10%/100)Bags = ceil(final volume / 0.6)Quick Shed Base Bag Counts
| Shed base | yd3 | 40 lb bags | 60 lb bags | 80 lb bags |
|---|---|---|---|---|
| 6 x 8 ft | 0.65 yd3 | 59 | 40 | 30 |
| 8 x 10 ft | 1.09 yd3 | 98 | 66 | 49 |
| 10 x 12 ft | 1.63 yd3 | 147 | 98 | 74 |
| 12 x 16 ft | 2.61 yd3 | 235 | 157 | 118 |
These fixed reference examples use 4 in thickness, one 10% allowance and 0.30/0.45/0.60 ft3 yield for 40/60/80-lb bags. Bags use unrounded volume, rounded up once; displayed yards are rounded separately. Confirm the actual product label. The live calculator uses your selected dimensions, units and bag size.
Example Shed Bases
Shed Base Thickness Guide
| Project | Planning thickness | Note |
|---|---|---|
| Light storage shed | Specified design | The 4 in example is arithmetic only; confirm bearing, base and shed-maker requirements. |
| Mower or equipment shed | Specified design | Point loads, reinforcement, and base prep need closer review. |
| Shed with ramp pad | Separate sections | Calculate the main slab and ramp or landing separately. |
| Poor soil or frost area | Confirm locally | Soil, drainage, frost, and code can override a simple estimate. |
Before You Order
- Use the finished pad size, not only the shed footprint.
- Include any border, ramp landing, or separate access pad.
- Confirm gravel base, compaction, drainage, and anchors.
- Compare ready-mix when the result reaches dozens of bags.
Shed Base Buying Guide
For a complete shed-specific walkthrough, use the written guide after the calculator. It covers 8x10, 10x12, and 12x16 shed base examples, 40/60/80 lb bag counts, ready-mix material cost, gravel base checks, backyard access, anchors, drainage, and quote questions.
Open the shed base concrete mix calculator guide before treating the material estimate as an installed project budget. For choosing slab thickness, use the concrete slab thickness guide. If backyard access is tight, compare chute, wheelbarrow, buggy, and bagged-concrete options before ordering.
Frequently Asked Questions
Disclaimer: This calculator is for concrete material planning only. Site conditions, base preparation, reinforcement, drainage, joints, form accuracy, and local building rules can change actual requirements. Consult a qualified contractor or engineer for structural work.