Reference chart

Concrete for a shed slab, by size

A 4 in slab for an 8x10 shed is 1.09 cubic yards, or 49 bags of 80 lb mix. A 10x12 slab is 1.63 yards (74 bags), which is past the point where ready-mix is usually the better buy.

By the ShedSizer editors · Updated 2026-09-24 · Researched from manufacturer specifications, published code summaries and verified owner reviews

Slab equals the shed footprint, with 10 percent added for waste and uneven subgrade. An 80 lb bag yields 0.6 cu ft and a 60 lb bag 0.45 cu ft.

Shed	Sq ft	4 in yd³	4 in 80 lb bags	4 in 60 lb bags	6 in yd³	6 in 80 lb bags
4x4	16	0.22	10	14	0.33	15
3x6	18	0.24	12	15	0.37	17
4x6	24	0.33	15	20	0.49	23
5x5	25	0.34	16	21	0.51	23
5x6	30	0.41	19	25	0.61	28
4x8	32	0.43	20	27	0.65	30
6x6	36	0.49	23	30	0.73	33
5x8	40	0.54	25	33	0.81	37
4x10	40	0.54	25	33	0.81	37
6x8	48	0.65	30	40	0.98	45
7x7	49	0.67	30	40	1.00	45
5x10	50	0.68	31	41	1.02	46
6x10	60	0.81	37	49	1.22	55
7x9	63	0.86	39	52	1.28	58
8x8	64	0.87	40	53	1.30	59
7x10	70	0.95	43	58	1.43	65
6x12	72	0.98	45	59	1.47	66
7x11	77	1.05	48	63	1.57	71
8x10	80	1.09	49	66	1.63	74
7x12	84	1.14	52	69	1.71	78
6x14	84	1.14	52	69	1.71	78
8x12	96	1.30	59	79	1.96	89
7x14	98	1.33	60	80	2.00	90
10x10	100	1.36	62	82	2.04	92
8x13	104	1.41	64	85	2.12	96
8x14	112	1.52	69	92	2.28	103
10x12	120	1.63	74	98	2.44	110
8x15	120	1.63	74	98	2.44	110
8x16	128	1.74	79	105	2.61	118
10x14	140	1.90	86	115	2.85	129
12x12	144	1.96	89	118	2.93	132
8x18	144	1.96	89	118	2.93	132
10x16	160	2.17	98	131	3.26	147
8x20	160	2.17	98	131	3.26	147
12x14	168	2.28	103	137	3.42	155
10x18	180	2.44	110	147	3.67	166
12x16	192	2.61	118	157	3.91	177
14x14	196	2.66	120	160	3.99	180
10x20	200	2.72	123	163	4.07	184
12x17	204	2.77	125	167	4.16	187
12x18	216	2.93	132	176	4.40	199
14x16	224	3.04	137	183	4.56	206
12x20	240	3.26	147	196	4.89	220
10x24	240	3.26	147	196	4.89	220
14x20	280	3.80	172	229	5.70	257
12x24	288	3.91	177	235	5.87	264
16x20	320	4.35	196	261	6.52	294
12x30	360	4.89	220	294	7.33	331

Anchors and tools for a slab

Researched picks spread from budget to premium.

Ahniiqo 1/2 x 3-3/4 inch Wedge Anchors Ahniiqo $12.99 Check price on Amazon

Larnorje 6 Pack Ground Earth Anchors with Drive Steel Stool LARNORJE $39.99 Check price on Amazon

Arrow Shed AK4 Earth Anchor Kit Arrow $58.22 Check price on Amazon

Johnson Level & Tool 40-6517 Self-Leveling Rotary Laser System Johnson $392.91 Check price on Amazon

Prices change often; the button shows today's price on Amazon.

Other shed reference charts

Frequently asked questions

When should I order ready-mix instead of bags?

Once a job passes roughly a cubic yard and a half, about 60 to 70 bags of 80 lb mix, ready-mix is usually competitive even with short-load fees, and it gives a far more consistent slab than batches mixed by hand over several hours.

This page is researched guidance, not professional engineering, legal or building-code advice. Sizes, loads and permit rules vary by product and by town: check your local code and the kit manufacturer's instructions before you build.