How to estimate concrete work before the truck is on the road
Concrete is estimated by the cubic yard: multiply slab square footage by thickness in feet and divide by 27 to get yards, order 5 to 10 percent extra, price base, reinforcement, and forms, add the pour-day crew at a loaded rate, and divide the total cost by one minus your target margin. A 480 square foot residential driveway priced this way typically quotes $10 to $14 per square foot. Concrete punishes estimating mistakes uniquely: once the truck pours, there is no ripping out a line item.
Step by step
- Convert the slab to cubic yards. Square feet times thickness in feet, divided by 27: a 480 square foot driveway at 4 inches is 480 times 0.333, which is 160 cubic feet, or 5.9 yards. Order 6.5 to cover subgrade variation and spillage, because coming up half a yard short mid-pour means a cold joint and a short-load fee. Ready-mix runs about $178 a yard, and suppliers commonly add $75 to $150 in short-load fees under their minimum.
- Specify the mix, not just the yards. Residential flatwork typically calls for 3,000 to 4,000 psi, with air entrainment required in freeze-thaw climates and fiber mesh additive available at about $9.50 a yard. Exterior slabs in cold regions should be 4,000 psi air-entrained or the surface will scale in three winters and the callback will find you. Put the psi on the estimate; it is a spec the customer can compare bids on.
- Price the base and subgrade work. A 4 inch compacted gravel base under the slab is its own volume calculation, about 6 yards at $43 a yard for that same driveway, plus excavation and compaction hours. Poor subgrade is the number one cause of cracked flatwork, so the base line is not the place to sharpen a pencil. Haul-off of spoil has dump fees; price them.
- Take off forms, reinforcement, and joints. Form lumber at $1.12 a linear foot around the perimeter with stakes at $2.40 each, welded wire mesh at $0.36 a square foot or number 4 rebar at $0.96 a foot on 18 inch centers for heavier duty, and expansion joint at $0.87 a foot where the slab meets existing concrete. Control joints get cut at roughly quarter of slab thickness in depth, spaced 24 to 36 times the thickness in inches. These lines add several hundred dollars and all of them are visible to an inspector or a lawyer later.
- Build the pour-day crew and timeline. Concrete work is two different days: forming and prep at a normal pace, then pour day, where the truck's schedule owns you and finishing cannot stop until the slab says so. A 6.5 yard driveway wants three workers: screed, bull float, edge, joint, then broom finish, with the crew on site from truck arrival to final cure protection. Estimate 40 to 45 crew-hours across both days at a loaded rate near $55 and treat overtime on a slow-setting day as a real risk line.
- Add sealing, curing, and weather protection. Cure-and-seal at about $0.19 a square foot protects the surface and is a legitimate line item, as is blanket protection for cold weather or evaporation control for hot wind. Weather moves pour dates, and a canceled truck can carry a fee. State a weather clause so a reschedule is a calendar event, not a contract fight.
- Divide cost by one minus margin. Materials plus crew labor plus disposal equals cost; the quote is cost divided by (1 minus margin). At a 30 percent margin, $4,198 of cost divides by 0.70 into a $5,997 quote, and rounding to $6,000 makes the driveway $12.50 a square foot. The multiply-instead-of-divide mistake yields $5,457 and a 23 percent margin, which on concrete's weather risk is not enough.
- Write exclusions and get the signature before scheduling the truck. Exclude rock excavation, unsuitable subgrade remediation, pump truck fees if access changes, and utility conflicts, each with a unit price where possible. Require the signed estimate and deposit before the ready-mix order goes in, since the material is perishable and the order is a commitment. A line-item estimate the customer signs on their phone gets the truck scheduled days sooner.
The concrete pricing formula
(Yards times ready-mix price, ordered with 5 to 10 percent cushion) plus base yards, reinforcement, forms, and sealer equals materials; prep-day plus pour-day crew-hours times the loaded rate equals labor; quote equals (materials plus labor plus disposal) divided by (1 minus margin), so a 30 percent margin divides by 0.70. Markup and margin diverge here as everywhere: 30 percent added to cost produces roughly a 23 percent margin because the added percentage is measured on cost rather than the final price. Concrete's weather and short-load risks deserve the full division.
A 20 by 24 foot driveway, 480 square feet at 4 inches thick: that is 160 cubic feet, or 5.9 yards, so you order 6.5 yards with a cushion, and at $178 a yard the concrete is $1,157. Add 6 yards of gravel base at $43 ($258), welded wire mesh at $0.36 a square foot ($172.80), form lumber and stakes ($170.56), expansion joint ($38.28), and cure-and-seal at $0.19 a square foot ($91.20), and materials total about $1,888. A three man crew forms and preps one day, then pours and finishes the next, roughly 42 crew-hours, which at a $55 loaded rate is $2,310. Cost comes to $4,198. Divide by 0.70 for a 30 percent margin and the quote is $5,997, call it $6,000, which is exactly $12.50 a square foot.
Cost factors concrete contractors price for
Access for the truck
If the chute reaches, placement is fast; if it does not, you are pricing a pump truck at several hundred dollars minimum or buggying mud at a heavy labor penalty. Wheelbarrow placement past 20 or 30 feet also risks cold joints on hot days. Confirm truck access at the walkthrough and write the assumption into the estimate.
Thickness and use
A 4 inch patio and a 6 inch garage slab differ by 50 percent in yardage on identical footprints, and vehicle-rated slabs want heavier reinforcement, with rebar at $0.96 a foot instead of mesh at $0.36 a square foot. Ask what will park on it before quoting. Thickness is the easiest place for two bids to secretly describe different slabs.
Demolition and haul-off
Breaking out an existing driveway is jackhammer or skid steer hours plus tonnage at the dump; broken concrete is dense and disposal is priced by weight. Tear-out often rivals the new pour in labor. Price removal as its own line with a load estimate.
Weather windows
Cold weather adds blankets, accelerators, and risk; hot windy weather accelerates set and demands more finishers moving faster. Both extremes can force reschedules with the batch plant. Carry a weather clause and, in marginal seasons, a modest contingency in the margin rather than promising a date you cannot own.
Finish and flatwork extras
Broom finish is the base; exposed aggregate, stamping, and coloring multiply both material and finishing labor and deserve their own quote tier. Sealer at $0.19 a square foot and saw-cut joints are small lines customers notice when a competitor skips them. The finish spec belongs on the estimate in words the customer can compare.
Frequently asked questions
How many yards of concrete do I need for a slab?
Multiply square footage by thickness in feet and divide by 27: a 400 square foot patio at 4 inches is 400 times 0.333 divided by 27, about 4.9 yards. Order 5 to 10 percent extra for subgrade variation and spillage, because running short mid-pour creates a cold joint and a second delivery fee. Ready-mix runs about $178 a yard, with short-load fees when you order under the supplier's minimum.
What margin should concrete work carry?
Concrete carries weather risk, perishable material, and a pour day you cannot pause, on top of normal overhead of 15 to 25 percent of revenue, so experienced flatwork contractors price at 30 to 40 percent gross margin by dividing cost by 0.60 to 0.70. A 10 percent markup is one rained-out truck or one extra yard away from a loss. Price so a bad day is absorbed, not fatal.
Mesh or rebar in a driveway?
Welded wire mesh at about $0.36 a square foot handles typical passenger vehicle driveways over well-compacted base, while number 4 rebar on 18 inch centers, about $0.96 a linear foot, is the upgrade for heavier loads, questionable subgrade, or thicker slabs. Either way, reinforcement controls crack width; it does not prevent cracking, which is what control joints are for. Spec it on the estimate so bids compare honestly.
Why do concrete bids vary so much per square foot?
Because thickness, psi, base depth, reinforcement, and finish are invisible in a lump-sum number: a 4 inch, 3,000 psi slab on 2 inches of base with mesh is a genuinely different product from a 5 inch, 4,000 psi air-entrained slab on 4 inches of compacted base with rebar. Residential flatwork commonly ranges $8 to $16 a square foot across those specs. Ask any low bid to state its spec in writing.
How do I get the estimate out before the customer cools off?
Staxen's Eddie drafts it by voice: say the dimensions, thickness, base, and finish, and Eddie produces a priced line-item estimate you review and text for e-signature, with the deposit collectable on the same page before you schedule the truck. Eddie is $59 per month, first job free, no card required. Ivy the Invoicer, $59, handles the progress and final invoices when you pour in stages.
Start free with Staxen: your first job is on us, no card required.