In short
- A seawall cap concrete calculator turns the wall length and the cap's width and depth into cubic yards: length x width x depth, divided by 27.
- The exact volume is always short of what you order. We add an order cushion of 5 to 15% (our planning assumption) and round up to the next quarter yard.
- An 85 ft wall with a 14 x 20 in cap holds about 6.1 cubic yards, so roughly 6.5 to 7.25 yards to order: one truck.
- This is geometry for planning. The sealed drawings set the cap size, the steel and the pour plan.
On this page
This seawall cap concrete calculator is for Cape Coral canal-front owners who want to know roughly how much concrete the cap of a new wall takes, so a quote or a delivery ticket does not come as a surprise. It uses geometry only, with no prices. It pairs with our seawall backfill calculator and our seawall length calculator.
En español: calculadora de concreto para la tapa del muro en Cape Coral
| Your numbers | Result |
|---|
Example: 85 ft of wall, 14 x 20 in cap, no returns. Illustrative numbers, not a City standard.
How the concrete is counted
- Cross-section.
Cap width in inches times cap depth in inches, divided by 144, gives square feet. A 14 x 20 in cap is 280 / 144 = 1.94 sq ft.
- Cubic feet.
Square feet times the total length in feet. 1.94 x 85 ft = 165.3 cu ft.
- Cubic yards.
Divide by 27. 165.3 / 27 = 6.12 cu yd.
- Cushion.
Multiply by 1.05 for the low end and 1.15 for the high end (our planning assumption): 6.43 and 7.04.
- Round up.
Plants deliver in whole quarter yards, so each figure rounds up to 6.5 and 7.25 yd.
- Trucks.
Divide by about 10 yd per full truck and round up. Both ends are one truck.
Concrete in common cap sections
| Cap section | Sq ft | Yd per 100 ft |
|---|---|---|
| 8 x 12 in | 0.67 | 2.5 |
| 12 x 12 in | 1.00 | 3.7 |
| 12 x 18 in | 1.50 | 5.6 |
| 16 x 24 in | 2.67 | 9.9 |
These are example cross-sections, not City standards. The exact cap is on your sealed drawings. Yards per 100 ft are net of any cushion.
The drawings and the pour plan come first
The sealed drawings govern. The engineer certifies the cap reinforcing and its placement, and the City reviews the permit. Read what gets certified in our Cape Coral seawall design standards guide, and see how the schedule runs in our seawall replacement timeline.
If the cap will be raised or the wall has returns at the property lines, those add length. Our seawall cap height calculator compares a cap elevation with NOAA water levels, and the permit guide covers the approvals.
Questions to ask your contractor
- What are the cap width and depth, and what concrete strength is on the drawings? Use the inches in this calculator.
- How many yards will you order, and how much cushion is in that? Compare with the 5 to 15% range here.
- Will the cap be poured in one day or in sections? Long walls often are, and weather can move the date.
- Who handles the cap inspection and the engineer's certification?
Next step: get a written quote
This tool estimates a volume, not the price or the job. We are a referral service, not a contractor; we connect visitors with independent local providers. Use the form below to ask independent local contractors for a written quote, and read how to choose a seawall contractor first.
Sources
- City of Cape Coral: Engineering Design Standards (draft, June 2026), section H Seawalls: the standard sheets that show the cap on precast and vinyl walls. Read the final adopted version.
- City of Cape Coral: Seawall Alternative Guideline, Residential: what the seawall permit application must show.
Concrete volume is length x width x depth (geometry). The 5 to 15% cushion, the quarter-yard rounding and the 10 cu yd truck load are our planning assumptions.
Frequently asked questions
How do I calculate the concrete for a seawall cap?
Multiply the cap width by its depth to get the cross-section, multiply by the wall length, and divide cubic feet by 27 to get cubic yards. For example, a 12 by 18 inch cap is 1.5 square feet, so each foot of wall holds 1.5 cubic feet and each 100 feet holds about 5.6 cubic yards. Read the real cap size from the sealed drawings.
How much extra concrete should I order?
There is no published rule for caps. Our planning assumption is a cushion of 5 to 15% over the exact volume, because forms are not perfectly true, the ground side can run slightly over and a short load is a problem. The calculator also rounds up to the next quarter yard. Your contractor and the concrete plant decide the actual order.
How many trucks will a seawall cap pour take?
Our planning figure is about 10 cubic yards per full truck, so most single-family canal walls fit in one or two loads. Plants set their own limits, and a long wall may be poured in sections on different days, so ask your contractor how the pour will be split.
Does the calculator include rebar and the panels?
No. It counts only the concrete in the cap. The steel inside the cap and its placement are part of what the engineer certifies, and the panels, tiebacks and fill are separate items. See our guide to Cape Coral seawall design standards for what gets certified.
Where do I find my cap dimensions?
On the sealed drawings for your wall. The City of Cape Coral publishes its seawall standard sheets in its Engineering Design Standards, section H, and your engineer shows the cap on the permit drawings. Ask your contractor for the cap width and depth in inches.