Enter your median or traffic island shape and dimensions to instantly calculate concrete volume in cubic yards, bag counts, and an estimated material cost. Supports rectangular, tapered, and oval islands.
Free to use
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No sign-up required
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Formulas verified against AASHTO & ACI 318
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Imperial & metric supported
✓ 3 island shapes: rectangular, tapered, oval✓ Bag count & ready-mix volume✓ Cost estimator included✓ Last verified May 2026
The longest dimension of the island, measured at the base.Please enter a valid length greater than 0.
Maximum width of the island measured at the base (widest point for ovals).Please enter a valid width greater than 0.
Width at the top surface of the tapered median (narrower than base).Please enter a valid top width greater than 0.
Height of the raised median from base to top surface. Standard: 6 inches.
Please enter a valid curb height greater than 0.
Use 10% for rectangular, 12–15% for tapered or oval shapes.
$
Leave blank to skip cost estimate. US average: $100–$150/yd³ for ready-mix.
Results appear instantly. No sign-up required.
Your Concrete Estimate
Concrete Volume (with waste)
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Cubic Yards (yd³)
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Cubic Feet (ft³)
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Cubic Meters (m³)
Bags Required (includes waste)
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40 lb bags
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60 lb bags
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80 lb bags
—Area (sq ft)
—Area (m²)
—Curb Height
—Waste Factor
Estimated Material Cost
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Concrete material cost only. Add forming, finishing, rebar, and labor ($3–$6/ft²) for a full project budget. Use our Full Project Estimator for a complete breakdown.
How to Use This Concrete Median / Traffic Island Calculator
Select your island shape.
Use Rectangular for any straight-sided barrier median with vertical curb faces. Use Tapered / Mountable for medians with angled sides that are wider at the base than at the top — measure both the base width and the top width. Use Oval / Elliptical for round-nose or teardrop islands — measure the full length along the centerline and the widest point across the middle.
Measure all dimensions from the base.
For length and width, always measure at grade level — the base footprint is what determines concrete volume. Do not measure at the top surface of a tapered median and use that as your only width; you will underorder concrete significantly. For oval islands, measure from tip to tip along the centerline for length, and full width at the widest belly for width.
Enter curb height and select a waste factor.
Most state DOT specs call for a 6-inch standard curb height. Use the quick-select buttons for common heights. Set waste to 10% for rectangular medians and 12–15% for tapered or oval work where form complexity and overspill are higher. Do not go below 10% — you cannot make a second concrete order mid-pour without creating a structural cold joint.
Use cubic yards for ready-mix orders; bag count if you're doing small repairs.
Any island larger than about 3 × 10 ft at 6-inch height crosses the threshold where ready-mix is the only practical choice. Give your ready-mix supplier the cubic yards figure. The bag count output is useful for small nose islands or repair patches only — bagging out a 30-foot median is a logistical nightmare you do not want to experience firsthand.
⚠ Pro Tip: The single most common mistake contractors make with median work is not accounting for the curb reveal separately from the interior slab. If your median design has an integral curb-and-slab (poured monolithically), calculate the full volume including the slab thickness beneath the curb height. If the curb sits on an existing slab, calculate curb volume only. This calculator handles the curb volume — adjust accordingly if you have an integral slab beneath.
Concrete Median Volume Formula
The correct formula depends entirely on the cross-sectional shape of your island. Using the wrong formula — most often treating a tapered median as rectangular — is the primary cause of underordering on median jobs.
Shape
Formula
Example
Result (no waste)
Rectangular
L × W × H ÷ 27
30 ft × 6 ft × 0.5 ft
3.33 yd³
Tapered
L × ((W_base + W_top) ÷ 2) × H ÷ 27
30 ft × ((6 + 4) ÷ 2) × 0.5 ft
2.78 yd³
Oval / Elliptical
π × (L/2) × (W/2) × H ÷ 27
π × 15 × 3 × 0.5 ft
2.62 yd³
Common Median Size Reference Table
Pre-calculated concrete volumes at 6-inch curb height, no waste factor. Add 10–15% for real-world ordering.
Island Size
Shape
Curb Height
Cubic Yards
80 lb Bags
10 × 4 ft
Rectangular
6 in
0.74
34
20 × 4 ft
Rectangular
6 in
1.48
67
30 × 6 ft
Rectangular
6 in
3.33
150
50 × 6 ft
Rectangular
6 in
5.56
250
20 × 4 ft (base), 2 ft top
Tapered
6 in
1.11
50
30 × 6 ft (base), 4 ft top
Tapered
6 in
2.78
125
20 × 6 ft
Oval
6 in
1.74
79
30 × 8 ft
Oval
6 in
2.62
118
40 × 10 ft
Oval
6 in
5.82
262
10 × 4 ft
Rectangular
8 in
0.99
44
30 × 6 ft
Rectangular
8 in
4.44
200
All volumes calculated from base footprint. Add waste factor before ordering. Bag counts use 80 lb bags (0.60 ft³ yield) and are always rounded up.
Curb Height Selection Guide
Curb height is the single variable with the most design, safety, and regulatory implications for median work. Choosing the wrong height causes drainage problems, accessibility failures, or vehicles mounting the median when they shouldn't be able to.
Standard curb height profiles for raised medians and traffic islands in US site work.
Curb Height
Profile Type
Typical Application
Vehicle Mountable?
Notes
3 in (75 mm)
Rollover / Mountable
Pedestrian crossing noses, fire lanes
Yes
ADA-compliant for emergency vehicle access. Easy to roll over; provides minimal physical separation.
6 in (150 mm)
Standard Barrier
Residential & arterial medians, traffic islands
No
Most common DOT specification. Provides effective vehicle separation. AASHTO recommended for most urban medians.
8 in (200 mm)
High Barrier
High-speed arterials, freeway interchange noses
No
Used where high-speed errant vehicle containment is a design criterion. Requires heavier forming.
21–27 in
Jersey/F-Shape Barrier
Divided highway medians, bridge barriers
No
Structural barrier — requires separate structural analysis. Volume is calculated from the true trapezoidal or F-shape cross-section, not this calculator.
📐 Design Note: Most state DOTs require 6-inch (Type B) curb for any median adjacent to travel lanes carrying traffic above 25 mph. Using 3-inch rollover curb on a 35 mph arterial because it's "easier to form" is a design defect that will come back as a liability claim when a vehicle mounts the island. Check your governing DOT standard drawings before specifying height.
5 Common Mistakes When Estimating Median Concrete
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Using top width for a tapered median instead of average width. A tapered median is wider at the base than at the top. Using only the top width in your calculation can underestimate concrete volume by 15–30% depending on the taper angle. Always average the base and top widths. This calculator does it correctly — manually doing this wrong is how contractors end up short on a pour.
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Forgetting the interior slab when calculating a monolithic median pour. Many raised medians are poured monolithically — curb and interior slab in one pour. The curb height you see above grade is not the full concrete depth. If there's a 4-inch slab beneath the finished surface, your actual concrete height is curb reveal + slab thickness. Failing to account for the slab can cause a 40–60% underestimate on thick island sections.
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Skipping waste factor on complex-shaped islands. Oval and tapered medians require precise forming with curved or angled formwork that flexes under concrete pressure, causing slight overruns. At minimum 12%, ideally 15%, waste factor on non-rectangular work. Running out of concrete mid-pour on a median creates a cold joint — a structural defect that will crack at the joint within the first freeze-thaw season.
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Ordering bagged concrete for any median over 10 linear feet. The labor calculus on bagged concrete for medians is brutal. A 20 × 4 ft rectangular median at 6-inch height needs roughly 67 bags of 80 lb mix — that's 2.7 tons of bags to hand-mix and place on a job site where you likely have traffic control costs per hour. Ready-mix is always the right call unless you're doing a small repair. The short-load fee from a ready-mix plant is far cheaper than the labor to bag out a full median.
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Not accounting for expansion joints in form layout before calculating pour sequences. A 50-foot median needs expansion joints every 20 feet — meaning you have three separate pour segments of 20, 20, and 10 feet. These joints require stop-boards in your formwork, and each segment must be calculated and ordered independently if poured on different days (different batch mixes must match). Calculate each segment's volume separately and confirm the sum matches your total before calling the plant.
Frequently Asked Questions
For a rectangular island: multiply length × width × curb height (all in feet) to get cubic feet, then divide by 27 for cubic yards. For tapered (trapezoidal cross-section) islands, use the average width formula: (top width + bottom width) ÷ 2 × height × length ÷ 27. For oval or elliptical islands, the formula is π × (half-length) × (half-width) × height ÷ 27. Always add a 10% waste factor to any figure you calculate.
The standard curb height for a raised concrete median in the US is 6 inches (150 mm), per AASHTO and most state DOT specifications. Mountable or rollover curbs used at pedestrian crossings are typically 3 inches. Some arterial medians use barrier curb (Type F or Jersey barrier profile) at 21–27 inches tall, which requires a separate structural calculation beyond the scope of this calculator.
For low-profile raised medians (6-inch curb height), DOT specs typically require #4 rebar at 12-inch on-center in both directions in the slab deck, plus longitudinal #4 bars in the curb face. For larger islands with a thicker interior slab (4–6 inches) supporting landscape elements or signage foundations, full slab reinforcement per ACI 318 applies. Never skip rebar on medians — traffic impact loads from errant tires are significant and unreinforced curbs crack and spall rapidly.
Most state DOTs specify Class B or Class C concrete — minimum 3,500 psi (24 MPa) compressive strength — for curbs and medians. In freeze-thaw climates, air-entrained concrete (5–7% air content) is required. Many specs also call for a water-cement ratio no greater than 0.45 and Type I/II cement. Do not use basic 3,000 psi bag mix for median work in cold climates — it will scale and deteriorate within 2–3 winters.
A mountable or tapered median has a trapezoidal cross-section — wider at the base, narrower at the top — which means the concrete volume calculation must use the average width, not just the top or bottom width. A rectangular (barrier) median has vertical sides and uses a simple L × W × H formula. Using the top width only for a tapered median will underestimate volume by 10–30% depending on the taper angle. This is one of the most common and costly errors on median concrete jobs.
For small traffic islands under about 0.5 cubic yards (roughly 5 × 3 ft at 6-inch height), bagged concrete is feasible. Above that, ready-mix is far more practical — the labor of mixing and placing hundreds of bags is prohibitive on any real site work project. Even a modest 20 × 4 ft median at 6-inch height requires over 67 bags of 80 lb mix. Order ready-mix for any median job of meaningful size and pay the short-load fee if necessary — it's still cheaper than the labor.
Use 10% for straightforward rectangular medians. For oval or tapered medians, use 12–15% to account for the geometric complexity and the difficulty of precisely forming curved edges. For medians with integrated curb-and-gutter in a single pour, 15% is appropriate. Never assume you can pour exactly to a calculated volume — formwork deflection and subgrade irregularities always absorb more concrete than the math suggests.
Minimum 7 days before any light pedestrian traffic. Most state DOT specs require 28-day compressive strength (typically 3,500 psi verified by cylinder tests) before vehicular traffic or opening the adjacent lane. In cold weather (below 50°F), curing time extends significantly — use insulated curing blankets and verify strength by testing, not just elapsed time.
No — expansion joints reduce the concrete volume by a negligible amount (the joint is filled with backer rod and sealant, not concrete). However, you do need to plan their location. For straight medians, place expansion joints every 20 feet. For curved or oval islands, space them every 15 feet along the arc. Skipping expansion joints causes restraint cracking within 1–2 freeze-thaw cycles and is the single most common field failure on median concrete work.
Painted nose islands have no raised concrete — they are pavement markings only. If you are converting one to a raised concrete island, the most common configuration is an oval or tear-drop shape 20–40 ft long and 4–8 ft wide at center, with a 6-inch curb height. A 30 × 6 ft oval at 6 inches yields approximately 0.52 cubic yards of concrete before waste. Use the Oval / Elliptical shape option in this calculator for tear-drop islands.
