Sandbag Calculator
Enter how long the sandbag wall needs to be and how deep the water could get against it. You'll get the number of bags, the sand to fill them and how wide the base must be, using the Army Corps of Engineers sizing.
- Army Corps of Engineers method
- Sand in yards and tons
- Feet or metric
2 What you need
Updates as you type| Dike height | 2 ft: your flood depth plus 1 ft of extra height |
|---|---|
| Bags per 100 ft | 2,100 |
| Shape | Corps pyramid, base 3 × height |
| Sand | 14 cubic yards at about 75 bags of 40 lb per yard, plus about 2 yd³ per 100 ft for the bags that hold the plastic down |
Keep the dike at least 8 ft from the house: NDSU warns a dike built against a wall pushes on the building. Seal the water side with plastic sheeting, never under the bags.
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Quick answer
A sandbag dike built Army Corps style, with a base three times its height, takes 600 bags per 100 ft at 1 ft high and 2,100 at 2 ft. For 50 ft of wall against 1 ft of water, build it 2 ft high: about 1,050 bags and 14 cubic yards of sand.
Sandbags for common wall lengths
| Wall length | 1 ft of water (2 ft dike) | 2 ft of water (3 ft dike) | Sand for 1 ft of water |
|---|---|---|---|
| 10 ft | 210 bags | 450 bags | 2.8 yd³ |
| 20 ft | 420 bags | 900 bags | 5.6 yd³ |
| 30 ft | 630 bags | 1,350 bags | 8.4 yd³ |
| 50 ft | 1,050 bags | 2,250 bags | 14 yd³ |
| 100 ft | 2,100 bags | 4,500 bags | 28 yd³ |
Corps pyramid dike (base 3 × height), height = flood depth + 1 ft. Sand at about 75 bags of 40 lb per cubic yard. Use the calculator above for your exact size.
How many sandbags per foot
The US Army Corps of Engineers sizes a sandbag dike as a pyramid whose base is three times its height. NDSU Extension turns the Corps rule into a formula. Worked the way NDSU's own example and the Corps table work out, it is: bags per foot of dike = (3 × H + 9 × H²) ÷ 2, where H is the height in feet. It matches the Corps table:
| Dike height | Bags per 100 ft (Corps, base 3 × height) | Bags per 100 ft (base 2 × height) |
|---|---|---|
| 1 ft | 600 | 600 |
| 2 ft | 2,100 | 1,700 |
| 3 ft | 4,500 | 3,000 |
| 4 ft | 7,800 | 5,500 |
A single row of bags one foot high, with no pyramid, takes about 300 bags per 100 ft, according to the Corps, but only where there is no current, floating debris or wave action that could topple it. NDSU Extension calls a base twice the height the minimum, and lists the narrower dike in the last column.
Worked example
You expect 1 ft of water against a 50 ft stretch. NDSU recommends building at least 1 ft higher than the expected water, so the dike is 2 ft high. At 21 bags per foot, 50 ft takes 1,050 bags, on a base 6 ft wide. At about 75 bags of 40 lb per cubic yard, that is 14 cubic yards of sand, about 20.8 tons.
How much sand
NDSU Extension estimates that a cubic yard of sand fills about 75 bags of 40 lb, with sand at 110 lb per cubic foot. Sand weighs 100 to 130 lb per cubic foot depending on how wet and packed it is, so your bags may come out heavier or lighter. The bag counts assume standard 14 × 24 inch bags filled about half full; smaller bags mean you need more of them. NDSU's own sand table comes out a little lower, about 25 cubic yards per 100 ft for a 2 ft dike against our 28, so this estimate errs on the side of extra. Add about 2 cubic yards per 100 ft for the bags that hold the plastic sheeting down.
Filling and placing the bags
- Don't stack bags against the house. NDSU says to leave at least 8 ft between the dike and any building, and to scrape away ice and snow first, because meltwater can run under the dike.
- Standard bags are about 14 × 24 inches. Fill them half to two-thirds full and leave them untied for a dike.
- Clear debris from the ground first and fill low spots before running bags along the full length. For a dike over about 3 ft, NDSU suggests a bonding trench 4 to 6 inches deep and 18 to 24 inches wide under it.
- Lay bags lengthwise, parallel to the flow, each partly overlapping the one before, and offset each row by half a bag so the joints don't line up.
- Walk on each bag to compact it, and fold the loose ends under.
- Seal the water side with polyethylene sheeting laid over the finished dike and held down with a row of bags. NDSU warns never to put plastic under the bags, because it makes the dike more likely to slide.
- Wear gloves, and keep treated bags away from your eyes and mouth.
Your county emergency management office can tell you where to get bags and sand during a flood. Sandbags reduce flood damage but, as the Corps puts it, do not guarantee a watertight seal. Follow local evacuation orders.
Frequently asked questions
How many sandbags do I need for 100 feet?
For a Corps-style dike, 600 bags at 1 ft high, 2,100 at 2 ft, 4,500 at 3 ft and 7,800 at 4 ft. A single row 1 ft high takes about 300.
How high should a sandbag wall be?
At least 1 ft higher than the water you expect, according to NDSU Extension, to allow for changes in the water level.
How many sandbags does a yard of sand fill?
About 75 bags of 40 lb, at 110 lb per cubic foot of sand (NDSU Extension).
How full should a sandbag be?
Half to two-thirds full, left untied, for a dike. Tied bags filled slightly fuller are for plugging holes or holding down sheeting, according to the Corps.
Last reviewed 2026-10-30. See how we calculate for our sources and assumptions.