How it works
The calculator converts the barrier height and length to feet, applies the US Army Corps of Engineers rule for bags per foot of barrier and rounds up to whole bags. With a fill figure it multiplies the bags by the sand per bag.
Pyramid: Bags per foot = (3 × H + 9 × H²) ÷ 2
Single row: Bags per foot = 3 × H
Bags = ⌈ Bags per foot × Length ⌉
Base width ≈ 3 × H (pyramid)
Sand = Bags × Sand per bag
H is the height in feet and the length is in feet; metric entries are converted first. ⌈ ⌉ means rounding up to the next whole bag. For a 2 ft pyramid, (3 × 2 + 9 × 4) ÷ 2 = 21 bags per foot, so a 100 ft barrier takes 2,100 bags – the figure in the Corps table.
Worked example
Inputs
- Stacking
- Pyramid (base 3 × height)
- Barrier length
- 100 ft
- Barrier height
- 2 ft
- Sand per bag
- 0.225 cu ft
Result
- Sandbags
- 2,100
- Fill sand
- 17.5 cu yd (472.5 cu ft)
- Base width
- 6 ft (72 in)
Common mistakes
- Building a tall single row. A single stack topples easily; above about 1 ft the Corps of Engineers uses a pyramid with a base about three times the height.
- Forgetting freeboard. The height should be above the expected water level, not equal to it.
- Filling bags to the top. The Corps recommends filling untied bags about one-half to two-thirds full so they can be shaped and pressed together.
- Ordering sand for exactly the bag count. Spillage and fuller bags use more; have extra sand and bags on hand.
- Treating a sandbag wall as a guaranteed seal. Sandbags reduce water damage but do not make a watertight barrier.
Assumptions and limits
- Pyramid bags per foot of barrier = (3 × H + 9 × H²) ÷ 2 with H in feet – the US Army Corps of Engineers (St. Paul District) formula, which gives 600, 2,100, 4,500 and 7,800 bags per 100 ft at 1, 2, 3 and 4 ft.
- A single row takes 3 bags per foot of length per foot of height (three bags high ≈ 1 ft, one bag length ≈ 1 ft), matching the Corps figure of 300 bags per 100 ft at 1 ft.
- The pyramid base is about 3 × the height; a single row is about one bag wide (three bags ≈ 2½ ft).
- Sand = bags × sand per bag; 0.225 cu ft per bag comes from the Corps figure of 1,200 bags per 10 cubic yards.
- Bags are rounded up to whole bags. This is a quantity estimate, not a flood-protection design.
Frequently asked questions
How many sandbags do I need for 100 feet?
Using the US Army Corps of Engineers table, about 600 bags for a barrier 1 ft high, 2,100 for 2 ft, 4,500 for 3 ft and 7,800 for 4 ft, built as a pyramid. A single row 1 ft high takes about 300.
How much sand fills a sandbag?
The Corps of Engineers St. Paul District counts about 1,200 bags of roughly 30 lb from 10 cubic yards of sand – about 120 bags per cubic yard, or 0.225 cubic feet per bag.
How wide should a sandbag wall be at the base?
The Corps rule of thumb is a base about three times the height, so a 2 ft barrier is about 6 ft wide at the bottom. Lay as many rows across the bottom as there are layers in height.
How high can a sandbag barrier be?
The Corps tables go up to 4 ft. Single rows are generally kept to about 1 ft. For anything higher, ask your local emergency management office or a qualified engineer.
Where can I get sandbags?
The Corps of Engineers brochure says local governments and flood control districts are responsible for keeping a supply of sandbags, so start with your city, county or emergency management office.
Sources
- Sandbags (brochure), St. Paul District — U.S. Army Corps of Engineers. Bags per foot of levee raise N = (3H + 9H²) ÷ 2 (H = 1, 2, 3, 4 ft → 6, 21, 45, 78); bags per 100 ft 600 / 2,100 / 4,500 / 7,800; single-width course 1 ft high 300 bags per 100 ft; base width 3 × height; 10 cu yd of sand ≈ 1,200 bags of about 30 lb (fill default 0.225 cu ft).
- Sandbagging Techniques (pamphlet, 2004), Northwestern Division — U.S. Army Corps of Engineers (copy hosted by Utah State University Extension). Same bags-per-100-ft table; single stack "generally not recommended above three courses or layers in height (approximately 1 foot)"; pyramid rule of thumb: 1 bag length ≈ 1 ft, 3 bags in width ≈ 2-1/2 ft, 3 bags in height ≈ 1 ft; fill bags one-half to two-thirds full.
- NIST Handbook 44, Appendix C – General Tables of Units of Measurement — National Institute of Standards and Technology. Exact unit definitions: 1 in = 2.54 cm, 1 yd³ = 27 ft³, 1 US gal = 231 in³, 1 lb = 0.45359237 kg.
Method reviewed November 5, 2026