Concrete Bag (Sack) Calculator
Find how many bags (sacks) of concrete mix you need. Your sizes can be in feet or metres. We count 30 kg and 25 kg bags.
Measure your project
Your answer
That makes 0.50 m³, or 0.65 cubic yards. We added 10% extra.
If you buy bags
A 30 kg bag makes 14 L, and a 25 kg bag makes 11.7 L. From the makers' Canadian data sheets.
If you order a truck (ready-mix)
Ask for 1.00 m³ (about 1.31 cubic yards). Ontario plant lists start at 1 m³, so we price at least that much.
This is a guide. For a slab, footing or post that holds weight, check your local building rules or ask a builder or engineer.
Which costs less?
But you must mix 36 bags by hand. That is 1.1 tonnes to lift.
Bag price: the middle of 8 prices at 5 Ontario stores, October 2026, before GST/HST. Your store may differ.
Quick answers
- 6 × 8 ft pad, 4 in thick
- 36 bags of 30 kg, with 10% extra. Or 43 bags of 25 kg.
- 30 kg bags per m³ and per yard
- 72 per m³ and 54 per cubic yard. For 25 kg bags it is 86 and 66.
- Bags on a pallet
- One Ontario store lists 56 bags of 30 kg per pallet. That is 1,680 kg, enough for about 0.78 m³.
- Price of a 30 kg bag
- $6.99 before tax, the middle of 8 prices at 5 stores, mostly in Toronto. A Windsor store charged $9.93, and a Whitehorse store $12.99.
How to work it out
- Measure your pad in feet, then multiply the length by the width.
- Multiply that by the thickness in inches, then divide by 12 to get cubic feet.
- Add 10% to cover spills and a bumpy base.
- Divide by 0.5 for 30 kg bags, or by 0.41 for 25 kg bags. Round up.
6 × 8 × 4 ÷ 12 = 16 cubic feet
16 + 10% = 17.6 cubic feet
17.6 ÷ 0.5 = 35.2 → 36 bags of 30 kg
17.6 ÷ 0.41 = 42.9 → 43 bags of 25 kg
Bag sizes sold in Canada
Canadian stores sell concrete mix in 30 kg bags. Some stores in BC and Alberta also sell 25 kg bags.
| Bag | Makes | Bags per m³ | Bags per cubic yard | Price |
|---|---|---|---|---|
| 30 kg concrete mix | 14 L (0.5 cubic foot) | 72 | 54 | $6.99 (5 stores) |
| 25 kg concrete mix | 11.7 L (0.41 cubic foot) | 86 | 66 | $8.29 (3 stores) |
| 30 kg fast-setting | 14 L (0.5 cubic foot) | 72 | 54 | $14.27 (2 stores) |
Before tax, October 2026. The 30 kg prices are from Ontario stores. The 25 kg price is from BC and Alberta. Few stores, so check yours.
We found no 20 kg or 40 kg bags of concrete mix. A 40 kg bag is Portland cement, which needs sand and stone. See the cement calculator.
Pound bags in US guides
US videos and guides count 80 lb, 60 lb or 50 lb bags. Quikrete's US concrete mix sheet says an 80 lb bag makes 0.6 cubic feet. A 60 lb bag makes 0.45, and a 50 lb bag makes 0.375.
Our 30 kg bag weighs about 66 lb and makes 0.5 cubic feet. So use 30 kg in the calculator, not a US bag size.
Bags for every 10 sq ft
Find your thickness to see how fast bags go. Thicker slabs eat bags quickly.
| Thickness | 30 kg bags per 10 sq ft | 25 kg bags per 10 sq ft | 30 kg bags per m² |
|---|---|---|---|
| 3 in (75 mm), thinnest floor slab | 5 | 6.1 | 5.4 |
| 4 in (100 mm), walk or patio | 6.7 | 8.1 | 7.1 |
| 5 in (125 mm), trucks (Manitoba) | 8.3 | 10.2 | 8.9 |
| 6 in (150 mm), trucks (Alberta) | 10 | 12.2 | 10.7 |
No extra added. Add 10% to your total, then round up.
Makers round up a little in their own tables. Sakrete says 10.7 bags for a 120 × 120 cm slab, 10 cm thick. Our sum gives 10.3.
Pallets, posts and tubes
An Ontario store sells 30 kg concrete in pallets of 56 bags. A Quebec store packs 30 kg mortar bags the same way.
A full pallet weighs 1,680 kg and makes about 0.78 m³, or 1.03 cubic yards. At 2 Toronto stores, 56 bags or more cost 10% less.
Fence posts and round tubes
The calculator above also counts bags for a footing, or for round holes such as piers and post holes. Tap "+ Add another part" to pick one. Posts and tube forms also have their own calculators. The fence post calculator counts post-mix bags for each hole. The sonotube calculator works out tubes and bell footings.
What the bags cost, and when a truck wins
We saw the same 30 kg bag at higher prices outside Toronto. Here is the 6 × 8 ft pad at each price.
| Store | One bag | 36 bags |
|---|---|---|
| Toronto: Home Depot and RONA | $6.98 | $251 |
| Toronto: Canadian Tire | $8.49 | $306 |
| Windsor ON: Home Depot | $9.93 | $357 |
| Whitehorse YT: Canadian Tire | $12.99 | $468 |
Regular prices before tax, read on 3 Oct 2026. One or two stores each, so treat them as rough. The Canadian Tire Toronto price is one reading.
The same pad takes 43 bags of 25 kg. At $8.29 (BC and Alberta, 3 stores), that is $356.
Past about 136 bags (1.9 m³), a ready-mix truck stays cheaper at our middle prices. From about 1.75 m³ up to there, the cheaper one swaps back and forth, so price both.
On smaller jobs, the truck's small-load fee is what makes bags cheaper.
The 36 bags weigh 1,080 kg. You lift each one, then mix it by hand or in a rented mixer.
Questions people ask
How many bags of concrete will I need?
Find the cubic feet, add 10%, then divide by 0.5 for 30 kg bags. A 6 × 8 ft pad, 4 in thick, takes 36 bags.
How many 30 kg bags of concrete fill 1 m³?
72 bags. Quikrete, Sakrete and Bomix all print 14 L per bag, so 72 bags make 1,008 L.
How much concrete does a 25 kg bag make?
11.7 L, or 0.41 cubic foot, says Quikrete's Canadian sheet. That is 86 bags per m³, or 66 per cubic yard.
How many yards of concrete are in a bag?
Very little. A 30 kg bag makes only 0.019 of a cubic yard.
How many bags of concrete are on a pallet?
An Ontario store lists 56 bags of 30 kg concrete per pallet. At 2 Toronto stores, you get 10% off for 56 bags or more.
How many 30 kg bags fit in a concrete mixer?
King Canada and Kushlan rate a 3.5 cu ft mixer for two 60–80 lb bags. That is about 2 bags of 30 kg. One maker rates its 6 cu ft mixer for 280 lb, about 4 bags of 30 kg.
What is 5 or 6 sack concrete?
It is a US ready-mix term: the number of 94 lb bags of cement in each cubic yard. Quikrete's US cement sheet uses 5 to 6 bags a yard for its own mix. Canadian plants name mixes by strength in MPa.
Where our numbers come from
- Bag sizes: Quikrete Concrete Mix, Canadian data sheet (30 kg = 14 L, 25 kg = 11.7 L)
- Bags per tube and post, walk thickness: Sakrete Concrete Mix (Canada) data sheet
- Bag size and fence posts: Bomix Concrete Mix data sheet (Quebec)
- Fast-Setting mix: Quikrete data sheet (bag sizes and fence posts)
- Store prices: Ontario Home Depot, RONA, Home Hardware and Chamberlain Timber Mart (Oct 2026)
- Bag price: 3 Canadian stores, 25 kg (Oct 2026; few prices)
- Bags per pallet: Dibbits listing (56 bags of 30 kg)
- Bags per pallet: Groupe Mortier listing (56 bags of 30 kg mortar)
- Floor slabs: BC Building Code 2018, Section 9.16 (at least 75 mm)
- Driveways and garage slabs: Concrete Manitoba (thickness, base, steel)
- Driveways, joints and slope: Concrete Alberta flatwork guide
- Extra for spills: Sakrete slab calculator (10%)
- Ready-mix price: the middle of 4 prices from 3 companies (25 MPa, Oct 2026, before tax)
- Small-load and winter fees: Dufferin Concrete 2026 price list (Ontario)
- Small-load fees: CBM Toronto-area price list
- Cement per cubic yard: Quikrete Portland Cement data sheet (5 to 6 bags of 94 lb)
- Bag sizes and weight: Quikrete Concrete Mix data sheet
- King Canada KC-15CM 3.5 cu ft mixer
- Kushlan 350DD 3.5 cu ft mixer
- Kushlan 600DD 6 cu ft mixer
Made by BuildersCount. Last checked 4 Oct 2026.
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