Concrete: Yield, Strength & Mix Basics
How many yards you need, what PSI to spec, and how to order the right mix.
Concrete is measured in cubic yards. Even small slabs go through concrete quickly — a 10×10 patio at 4″ deep needs about 1.25 yards. Ordering a half-yard short means paying for a return trip.
How do I calculate how much concrete I need?
Standard residential concrete is 3,000–4,000 PSI. Sidewalks and interior slabs are fine at 3,000 PSI; driveways, garages, and structural footings should be 4,000 PSI or higher with fiber or rebar.
One cubic yard fills a 4″ slab of about 81 sq ft, a 5″ slab of 65 sq ft, or a 6″ slab of 54 sq ft. Always order 5–10% extra to cover uneven subgrade and waste.
Ready-mix trucks usually require a minimum order (often 1 yard) plus short-load fees under 3 yards. For jobs under ½ yard, bagged mix is more economical — an 80 lb bag yields 0.6 ft³, so you'll need about 45 bags per yard.
What is concrete used for?
- Slabs, driveways, patios, sidewalks
- Footings and foundation walls
- Steps, curbs, and pads
- Structural columns and piers
Which types of concrete are there?
What else do people ask about concrete?
How many bags of concrete in a yard?
About 45 × 80 lb bags, 60 × 60 lb bags, or 90 × 40 lb bags.
What PSI should a driveway be?
4,000 PSI minimum, with rebar or fiber and a 4–6″ compacted gravel base.
How much concrete for a 10×10 slab?
About 1.25 cubic yards at 4″ deep, or 1.55 yards at 5″.