Table of Contents
- Volume equals length times width times thickness; convert everything to feet, then divide cubic feet by 27 to get cubic yards.
- Add roughly 5 to 10 percent for waste, spillage and uneven subgrade, and confirm with your supplier.
- An 80-pound bag yields about 0.6 cubic feet, so bagged mix is practical only for small pours.
- In New York, truck access, pump placement and building rules often matter as much as the volume itself.
- Structural pours, basement slabs and anything under a living space deserve a licensed professional and often a filing.
Concrete is sold by volume, and volume is where first-time estimators go wrong. A quick mental guess of a few bags turns into a half-poured slab, a cold joint and an emergency delivery. Order too much and you pay for a truck to dump a cubic yard on the street. Neither mistake is expensive in the abstract, but both are expensive in a city where truck access is limited and every hour on site is scheduled.
This guide gives you the formulas, worked examples and rules of thumb for estimating concrete for renovation projects, from a backyard patio to a basement floor. It also explains the practical issues that sit around the numbers in New York: access, protection, curing, hazmat and permits. If you want a broader budget tool, try our Renovation Estimation Calculator alongside this page.
1. The Core Formula
Concrete is measured in cubic yards in the United States. One cubic yard equals 27 cubic feet, because a yard is three feet and 3 times 3 times 3 is 27.
The basic formula for a rectangular slab is:
Volume in cubic feet = length (ft) x width (ft) x thickness (ft)
Then convert to cubic yards:
Cubic yards = cubic feet / 27
Thickness is the step most people miss. If your slab is 4 inches thick, divide 4 by 12 to get 0.333 feet before you multiply. A 6-inch slab is 0.5 feet. An 8-inch footing is 0.667 feet.
Worked example: a small patio
A patio that is 12 feet by 10 feet and 4 inches thick:
- 12 x 10 x 0.333 = 40 cubic feet
- 40 / 27 = about 1.48 cubic yards
- With a 10 percent waste allowance: about 1.63 cubic yards
You would typically order a little under 2 cubic yards, subject to the supplier's minimum load.
2. Volume for Other Shapes
Footings and walls
Use the same rectangular formula with the footing's width and depth, multiplied by its length. A 30-foot run of footing that is 16 inches wide and 8 inches deep:
- Width 1.333 ft, depth 0.667 ft
- 30 x 1.333 x 0.667 = about 26.7 cubic feet
- 26.7 / 27 = about 0.99 cubic yards
Round columns and piers
Use the circle formula: volume = pi x radius squared x height. A column that is 12 inches in diameter and 8 feet tall has a radius of 0.5 feet:
- 3.1416 x 0.5 x 0.5 x 8 = about 6.28 cubic feet
- That is about 0.23 cubic yards per column
Slabs with variable thickness
If the thickness varies because the subgrade slopes, measure at several points, average the thicknesses and use that average. For a sloped basement floor, break it into rectangles and calculate each one.
Triangles and irregular shapes
Divide the area into rectangles and triangles, calculate each, and add them. For a triangle, area equals one-half of base times height.
3. Quick Reference Table for Slabs
The table shows the volume for 100 square feet of slab at common thicknesses, before waste.
| Thickness | Cubic feet per 100 sq ft | Cubic yards per 100 sq ft |
|---|---|---|
| 3 inches | 25.0 | 0.93 |
| 4 inches | 33.3 | 1.23 |
| 5 inches | 41.7 | 1.54 |
| 6 inches | 50.0 | 1.85 |
| 8 inches | 66.7 | 2.47 |
To use it, divide your slab's area by 100 and multiply by the figure in the table. A basement floor that measures 20 by 25 feet, or 500 square feet, at 4 inches thick needs 5 x 1.23, which is about 6.2 cubic yards before waste.
4. Add a Waste Factor and Check the Subgrade
Real pours rarely match the math. Add a margin for:
- Spillage and the concrete that stays in chutes and pumps
- Forms that bow slightly under pressure
- Subgrade that is lower in places than you measured
- Thickened edges or footings that were not in your first sketch
- Small errors in measurement
A typical allowance is 5 to 10 percent, and many contractors use more for irregular or hard-to-measure pours. Ask your supplier what they recommend and what their minimum load and short-load charges are. Order slightly high for structural slabs, since running short in mid-pour can leave a cold joint.
Thickness and reinforcement
Thickness depends on use. Patios and walkways often use 4 inches, while slabs that carry vehicles or heavy loads are thicker and reinforced. Reinforcing steel or wire mesh, compacted gravel base and vapor barriers are not covered by the volume formula but belong in the plan. Structural specifications should come from a licensed professional.
5. Bags or a Truck?
Bagged mix is convenient for small jobs. The yield per bag is roughly:
| Bag size | Approximate yield | Bags per cubic yard |
|---|---|---|
| 40 lb | 0.3 cu ft | About 90 |
| 60 lb | 0.45 cu ft | About 60 |
| 80 lb | 0.6 cu ft | About 45 |
Using the patio example, 40 cubic feet at 0.6 cubic feet per 80-pound bag requires about 67 bags, or about 74 with a 10 percent waste allowance. That is roughly 5,900 pounds of bags to carry and mix, which is why most people order a truck at this scale.
Rules of thumb:
- Under about half a cubic yard: bags are fine.
- Between half a yard and a couple of yards: consider a small mixer or a short-load delivery, depending on access.
- Above that: order ready-mix, and plan the pour with help.
6. NYC Access, Protection and Logistics
The numbers are the easy part. In New York, getting concrete to the spot is the real project.
- Truck access: narrow streets, no driveway and alternate-side parking limit where a truck can stand. Street use may require permits or approvals; check with the relevant city agencies.
- Pumps and buggies: pours behind a row house or inside a courtyard often need a pump or hand carts.
- Building rules: co-ops and condos limit hours, require protection of elevators and halls, and often prohibit wet trades above or near other units.
- Weight: a cubic yard of concrete weighs roughly two tons, which matters for floors, balconies, roofs and sidewalk vaults. Structural capacity must be verified by an engineer.
- Noise and dust: demolition and cutting create noise and dust that building rules and the city's Noise Code regulate. Construction is generally limited to weekdays from about 7 AM to 6 PM unless a variance is approved, and many buildings are stricter.
Professional crews follow OSHA's respirable crystalline silica standard, and homeowners who hire out concrete cutting should ask how dust will be controlled. If you want a second opinion on logistics before you order, request a free estimate and we will look at access with you.
7. Curing, Moisture and What Goes on Top
Concrete does not simply dry. It cures through a chemical reaction that continues for weeks. Keep new concrete damp and protected from rapid drying for the first days, and avoid heavy loads until the specification allows. Many specs assume about 28 days to reach design strength.
If you plan to install flooring over a slab, moisture matters. Wood, vinyl and some adhesives are sensitive to residual moisture, and installers often test the slab before covering it. See our article on concrete drying and its impact on renovation for details, and our post on recycled water in concrete for sustainability context. Subfloor prep and leveling typically run about $2 to $8 per square foot as a 2026 planning range, and floor removal about $2 to $7 per square foot.
8. When a Concrete Job Needs a Permit or a Professional
Not every pour needs a filing, but many do. As a rule:
| Project | Typical approach |
|---|---|
| Garden path or small pad | Often DIY, check local rules |
| Patio or walkway at a house | Check local zoning and permits |
| Basement floor replacement or underpinning | Licensed professional and DOB filing |
| Structural slab, footing or foundation | Registered design professional, permit and inspections |
| Interior slab work in a co-op or condo | Board approval plus professional design |
In New York City, most construction work needs a Department of Buildings permit, and alterations are filed through DOB NOW: Build by a registered architect or professional engineer. The DOB's page on obtaining a permit explains the process, and Do I Need a Permit? gives a quick first answer. For other planning basics, see our guides to ten golden rules before starting your renovation and starting a renovation in the NY tri-state area.
9. Neighborhoods and ZIP Codes We Serve
Concrete work depends on the building. In the East Village (ZIPs 10003 and 10009), tenement walk-ups with tight stair access mean concrete is usually hand-carried or bagged, and structural floor work is rare. Williamsburg (ZIPs 11211, 11249 and 11206) has converted lofts, new waterfront condos and wood-frame row houses, where slab leveling and thin toppings over old floors are common.
Bayside (ZIPs 11361 and 11364) has detached homes, garden apartments and co-ops, where patios, steps and basement floors are typical. Stapleton (ZIP 10304) in Staten Island has Victorian houses, Stapleton Heights and new waterfront condos, with foundation and flood considerations in lower areas. East Meadow (ZIP 11554) in Nassau County has ranches and capes in the Town of Hempstead, where driveways, patios and garage slabs are common and permits come from the town. Nutley (ZIP 07110) in Essex County, New Jersey has older colonials and two-family homes, where permits come from the municipal construction office. See our pages for the East Village and Williamsburg.
10. Why Hire a Licensed Design-Build Team for Concrete-Related Work
The math in this article will get you a good estimate. It will not tell you what is under the old floor, whether the slab is level, how thick it really is or whether the building will allow a truck, a pump or a jackhammer. Those are the questions that determine cost and schedule in a New York renovation.
N.Y. Renovation Services is a licensed and insured design-build contractor serving the five boroughs, Long Island and nearby New Jersey. Residential remodeling in New York City requires a Home Improvement Contractor license from the Department of Consumer and Worker Protection, and our hiring checklist shows how to verify it.
How an in-house team helps with slabs and floors:
- Survey and layout: we measure real conditions, not just the plan, and note slope, cracks and moisture.
- Demolition and haul-away: selective demolition typically runs about $8 to $30 per square foot depending on access, floors and debris, and we plan stairs, containers and building hours.
- Hazmat and dust control: older floors may hide asbestos-containing tile or mastic, and cutting concrete creates silica dust. We test, contain and follow OSHA practices.
- Permits and board paperwork: we coordinate with the licensed design professional and handle co-op or condo submissions.
- Flooring and tile on top: leveling, moisture testing, waterproofing and installation are part of our focus services, so the slab and the finish are planned together.
- Itemized pricing: you see demolition, prep, materials and finishes as lines in a written contract, with no hidden fees.
DIY pours make sense for small, non-structural projects. They go wrong when the slab sits inside a building, supports a structure or will receive tile or wood flooring, because errors in level, thickness or moisture show up months later as cracked tile and lifting boards. We also donate 5 percent of total project cost to a nonprofit of the client's choice.
11. Next Steps: Get Your Free Estimate
If your project involves a slab, a basement floor or a floor that needs to be flat before tile or wood goes down, a site visit is the best next step.
- Sketch the area and note dimensions, thickness if known, and any cracks or damp spots.
- Photograph access routes: stairs, doors, hallways, courtyards and curb space.
- Gather your building's alteration agreement if you have a co-op or condo.
- Request a free estimate on our quote page or call (347) 455-1741, Monday through Saturday, 8 AM to 5 PM.
- Review a written, itemized proposal with demolition, prep, finishes and schedule.
For budget context, see our NYC renovation cost guide, and for a common project that often involves floors, see Kitchen Remodeling NYC. Calculating paint for the finished space? Our paint cost calculator guide covers that step, and the Renovation ROI Calculator helps you decide how much to invest.
Safety Note: All work follows OSHA 30 safety and EPA Lead-Safe practices for pre-1978 homes. Check local permit requirements before starting.
James - Lead Renovation Editor. With over 20 years in renovation and construction, James writes and edits our guides. More about James