Concrete Calculator
Estimate concrete for slabs and patios by cubic feet, cubic yards, bags, waste allowance, and ready-mix or bagged concrete cost.
Concrete Project Estimate
Planning estimate generated by Activity Accounts. This is not a contract or binding professional quote.
Concrete project and quote calculator
Estimate a rectangular slab, review a contractor quote, or build a detailed project price with editable local costs.
Save this project
Save the current mode, every calculator input, and a readable result snapshot in this browser.
Slab dimensions and concrete
Quantity snapshot
Additional rough allowances
Add optional planning amounts without opening the contractor cost model.
Quick estimate
Need more detail?
Contractor quotes
Attach this Check-mode quote to the current saved project for browser-local comparison.
Save this project before attaching contractor quotes.
Contractor quote and modeled allowances
Quote scope checklist
Check only items the proposal clearly confirms. The checklist organizes scope; it does not assign prices.
Quote check results
Differences may reflect access, excavation, reinforcement, forms, concrete strength, pumping, short-load charges, finishing, local labor, permits, insurance, warranty, or site conditions not represented here.
This tool organizes quote information for planning. It does not inspect the site, determine code requirements, or decide whether a contractor's price is fair.
1. Project and materials
The shared slab inputs above determine concrete quantity and ready-mix material cost.
Concrete material cost: $0.00
Materials subtotal: $0.00
2. Crew and labor
Loaded hourly cost is the business's total employment cost, including wages and applicable payroll taxes, insurance, benefits, and other employer costs.
Labor subtotal: $0.00 · Crew-hours: 0.00
3. Equipment
Equipment subtotal: $0.00
4. Other direct job costs
Other direct costs subtotal: $0.00
5. Overhead, contingency, and profit
A target margin is not the same as a markup. The calculator divides cost by one minus the target margin to produce the intended gross-margin percentage.
Built quote results
See full cost breakdown
Common concrete thickness assumptions
| Project | Common concrete thickness |
|---|---|
| Sidewalk | 4 inches |
| Patio | 4 inches |
| Shed slab | 4 inches |
| Driveway | 5 to 6 inches |
| Garage slab | 4 to 6 inches |
| Heavy equipment pad | 6+ inches |
Waste allowance
Default 10%. Concrete is hard to stretch once the pour starts. For small jobs, odd shapes, uneven ground, or first-time DIY projects, 10% extra is usually safer than ordering the exact calculated amount.
Concrete calculator FAQ
How many 80 lb bags are in a cubic yard?
One cubic yard is 27 cubic feet. An 80 lb bag yields about 0.60 cubic feet, so one cubic yard takes about 45 bags before waste.
Is bagged concrete cheaper than ready-mix?
Bagged concrete is convenient for small jobs. Ready-mix is often more practical for larger pours because bag counts get high quickly.
How thick should a concrete patio be?
Many patios are 4 inches thick, but soil conditions, reinforcement, loads, and local code can change the right answer.
How much concrete do I need for fence posts?
Post holes depend on hole diameter, depth, and post size. A dedicated fence/post calculator is planned; for now, use slab mode only for rectangular slabs.
Should I add waste to concrete?
Yes, a waste allowance helps cover uneven ground, measurement error, spillage, and small variations during the pour.
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