How to Estimate Concrete Work: Yardage, Rebar, Forms & Labor

Concrete estimating comes down to one thing: getting your quantities right. Every yard of concrete costs $130-$175 delivered, and every square foot of formwork, rebar, and finishing adds labor. Miss your yardage by two yards on a 12-yard pour and you're either paying for a short load or eating the cost of an extra truck. This guide covers the full process for estimating concrete work -- from calculating cubic yards to pricing the finished job.

The Cubic Yard Formula

Everything in concrete starts with cubic yards. Here's the formula:

Cubic Yards = (Length x Width x Thickness) / 27

All measurements in feet. The 27 comes from there being 27 cubic feet in one cubic yard (3 x 3 x 3).

Example: A 20' x 30' driveway at 4" thick:

• Convert 4 inches to feet: 4/12 = 0.333 ft
• Volume: 20 x 30 x 0.333 = 200 cubic feet
• Cubic yards: 200 / 27 = 7.41 yards

Always add a waste factor. For flatwork, add 5-10%. For footings and walls with more formwork, add 10-15%. That 7.41-yard driveway should be ordered as 8 yards. Concrete plants usually sell in half-yard increments, and a short load fee ($50-$100 per yard under the minimum) hurts more than an extra half-yard of mud.

Quick Reference: Thickness to Yards Per 100 Sq Ft

Thickness	Yards per 100 sq ft
4"	1.23 yards
5"	1.54 yards
6"	1.85 yards
8"	2.47 yards
12"	3.70 yards

Memorize the 4" number (1.23) and you can estimate most flatwork in your head on a site visit.

Concrete Material Costs

Concrete pricing varies by region and mix design, but here are 2025-2026 baseline ranges:

• Standard ready-mix (3000 PSI): $130-$160/yard delivered
• High-strength (4000-5000 PSI): $145-$180/yard delivered
• Fiber-reinforced: Add $8-$15/yard
• Color-added: Add $15-$30/yard
• Short load fee (under 6-8 yards): $50-$100/yard under minimum
• Pump truck (if needed): $800-$1,500 for a standard boom pump, plus $50-$75/yard pumped

Saturday pours and early-morning pours often carry surcharges. Check with your batch plant.

Rebar and Reinforcement

Most concrete work requires some form of reinforcement. The spec depends on the application:

Rebar

• #3 rebar (3/8"): Residential slabs, patios. Typically 18" or 24" on center both ways.
• #4 rebar (1/2"): Driveways, garage slabs, footings. 12" or 18" on center.
• #5 rebar (5/8"): Commercial slabs, walls, heavy structural.

Material cost: $0.50-$1.00/linear foot for #4 rebar. Figure your grid spacing, calculate how many bars you need in each direction, add overlap (18" minimum laps), and multiply.

Labor to tie rebar: A good ironworker or concrete crew can place and tie rebar for a typical residential slab at about 500-800 sq ft per day. Budget 0.015-0.025 man-hours per square foot for rebar placement on flatwork.

Welded Wire Mesh (WWM)

• 6x6 W1.4/W1.4 (6 gauge): Standard for sidewalks and light-duty slabs
• 6x6 W2.9/W2.9 (4 gauge): Driveways, garage floors

Material cost: $0.15-$0.30/sq ft for standard mesh. Faster to install than rebar but less structural. Mesh works fine for residential flatwork where the rebar spec is minimal.

Formwork

Forms hold the concrete in place while it cures. The cost depends on the type of work:

• Flatwork edge forms (2x4 or 2x6 lumber): $1.50-$3.00/linear foot installed. This covers the lumber, stakes, and labor to set and strip.
• Wall forms (prefab or plywood): $4-$8/sq ft of form face area for residential. Commercial form systems can be rented.
• Footing forms: $3-$6/linear foot for simple spread footings.
• Curb forms: $4-$8/linear foot.

Form lumber is often reusable for 2-3 pours. Factor that into your job costing, but bid it at full cost -- the savings on reuse are yours to keep.

Labor: The Biggest Variable

Concrete labor breaks down into several phases, each with different crew needs:

Labor Phases

1. Site prep / grading: 0.01-0.03 man-hours/sq ft. Depends on conditions.
2. Form setting: 0.02-0.04 man-hours/linear foot of forms.
3. Rebar / mesh placement: 0.015-0.025 man-hours/sq ft.
4. Pour day: You need enough crew to keep up with the truck. A typical residential flatwork pour needs 4-6 people.
5. Finishing: 0.02-0.05 man-hours/sq ft depending on finish type. Broom finish is fastest; stamped or exposed aggregate takes 2-3x longer.
6. Strip and cleanup: 0.01-0.02 man-hours/sq ft.

Burdened Labor Rates

• Finisher: $55-$85/hr burdened
• Laborer: $30-$50/hr burdened
• Foreman/lead: $65-$100/hr burdened

Use your actual burdened rates -- wages plus taxes, workers' comp, insurance, and benefits. Bare wages will make you low on every bid.

Common Project Cost Ranges

These are total installed costs (materials, labor, equipment) before your overhead and profit markup:

Project	Size	Direct Cost Range
Driveway (standard broom)	600 sq ft, 4"	$4,500-$7,500
Sidewalk	200 sq ft, 4"	$1,500-$3,000
Patio (stamped)	400 sq ft, 4"	$4,800-$8,000
Garage slab	600 sq ft, 5"	$5,000-$8,500
Residential foundation (monolithic)	1,500 sq ft	$8,000-$15,000
Retaining wall (4' tall)	50 linear ft	$8,000-$15,000

Building the Estimate Step by Step

1. Calculate yardage. Measure or take off from plans. Apply the formula. Add waste factor.
2. Get concrete pricing. Call your batch plant for current pricing on the mix design specified. Don't use last year's number.
3. Estimate reinforcement. Rebar or mesh based on spec. Calculate quantities.
4. Estimate formwork. Linear feet of edge forms or square feet of wall forms.
5. Estimate labor. Break it into phases. Apply man-hour factors. Multiply by burdened rates.
6. Add equipment. Pump truck, bobcat, vibrator rental, concrete saw -- whatever the job needs.
7. Add overhead and profit. Overhead is typically 10-18% for concrete contractors. Profit is on top of that. Your total markup should land you at a 20-35% gross margin depending on your market.

Mistakes That Sink Concrete Estimates

• Miscalculating thickness. Forgetting to convert inches to feet in the formula. Four inches is 0.333 feet, not 4 feet.
• No waste factor. Concrete doesn't pour perfectly to the edge of every form. 5-10% waste is real.
• Ignoring short load fees. If you need 5 yards and the plant minimum is 7, you're paying the fee. Budget for it.
• Underestimating finishing labor. Stamped concrete takes 2-3x the labor of broom finish. Decorative work requires experienced finishers at higher rates.
• Not accounting for weather. Cold weather adds blankets, curing compounds, and sometimes heated enclosures. Hot weather adds accelerants and more crew to finish before it sets.

Estimate Faster with Better Tools

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FAQ

How many cubic yards of concrete do I need for a 10x10 slab?

For a 10' x 10' slab at 4" thick: (10 x 10 x 0.333) / 27 = 1.23 cubic yards. Order 1.5 yards to account for waste and subgrade irregularities. At 6" thick, you'd need 1.85 yards -- order 2. Most batch plants have a minimum load of 1 yard, with short load fees kicking in under 6-8 yards depending on the plant.

What's the difference between 3000 PSI and 4000 PSI concrete?

PSI stands for pounds per square inch -- it's the compressive strength of the concrete after 28 days of curing. 3000 PSI is standard for residential flatwork like sidewalks and patios. 4000 PSI is specified for driveways, garage floors, and anything that takes vehicle traffic or heavier loads. 4500-5000 PSI is common for commercial and structural applications. The cost difference is typically $10-$20/yard between 3000 and 4000 PSI.

How do I price stamped concrete vs. regular flatwork?

Stamped concrete typically costs 2-3x more than standard broom-finish flatwork. The additional cost comes from: the stamps and stamp mats (tools), color hardener and release agent (materials at $0.30-$0.75/sq ft), and significantly more finishing labor. A broom-finish driveway might run $8-$12/sq ft installed. Stamped concrete on the same driveway runs $15-$25/sq ft. The labor is what kills you -- stamped work requires experienced finishers and the window to stamp is tight, so you need more hands on pour day.

Should I include subgrade prep in my concrete estimate?

Always. Subgrade prep -- grading, compaction, and gravel base -- is part of the job even if it seems minor. A standard 4" gravel base costs $1.50-$3.00/sq ft for material and placement. If the existing grade needs significant cut or fill, that's excavation work and adds real cost. Some concrete contractors sub out the grading; others self-perform. Either way, it needs to be in the estimate. Skipping it leads to either a change order (which the client hates) or eating the cost (which you should hate).