Estimate a broad ready-mix quantity before requesting a quote.
Use this general estimator for rectangular pads, paths, walls, trenches, or other pours when the immediate question is how much ready-mix volume to order.
Measure each differently sized section separately, then add the adjusted quantities. Keeping sections separate makes depth changes and irregular areas easier to review.
Match the estimate to the purchasing decision.
This broad calculator answers a volume question without assuming a slab use. Concrete Slab frames the same rectangular volume math around floor area and thickness; Concrete Bag converts volume to retail premix bags; Concrete Cost applies a supplier unit price.
Formula and calculation method.
Order volume = length × width × depth × (1 + waste percentage ÷ 100)Depth is converted from inches to feet for imperial calculations or centimetres to metres for metric calculations. The rectangular volume is converted to cubic yards or retained as cubic metres, then the waste percentage is applied.
Follow realistic concrete takeoffs.
Length 12 ft; width 10 ft; depth 4 in; waste 10%
Working: 12 × 10 × (4 ÷ 12) ÷ 27 × 1.10
Result: 1.63 yd³ to order (1.48 yd³ before waste)
Interpretation: The extra 0.15 yd³ provides a modest field allowance, but the supplier may require rounding to its delivery increment.
Length 5 m; width 3 m; depth 12 cm; waste 5%
Working: 5 × 3 × 0.12 × 1.05
Result: 1.89 m³ to order
Interpretation: This covers one constant-depth rectangle; curves or changing depths should be split into measured sections.
Turn the estimate into an order plan.
The headline quantity is volume, not truck count or weight. Ask the ready-mix supplier how it rounds orders and whether a short-load minimum applies.
Waste is a planning allowance, not a substitute for measurement. Compare base and adjusted volume and investigate large allowances before ordering.
Assumptions and common mistakes.
What the estimate assumes
- The measured shape is rectangular.
- Length and width use feet or metres while depth uses inches or centimetres as labeled.
- Waste is applied once to the base volume.
- Concrete density does not affect a volume-based ready-mix order.
Mistakes to avoid
- Entering depth in feet when the field expects inches.
- Measuring the excavation instead of the finished concrete shape.
- Combining sections with different depths into one average without checking it.
- Rounding each dimension before multiplying.
Handle unusual concrete plans explicitly.
A 0% allowance returns the exact modeled rectangular volume.
Divide it into rectangles and calculate each section; this tool does not infer curves or triangles.
The entered depth is treated as constant, so use surveyed sections or a defensible average depth.
What this estimate leaves out.
This estimate excludes form deflection, over-excavation, embedded objects, pump-line waste, supplier minimums, truck access, mix specification, reinforcement, labor, and structural design.
Concrete planning questions.
How do I calculate concrete volume?
Multiply finished length by width by depth using consistent units, convert to cubic yards or cubic metres, and then add the selected waste allowance.
How many cubic feet are in a cubic yard?
One cubic yard contains 27 cubic feet.
Should concrete depth be entered in inches?
In imperial mode, yes. In metric mode, enter depth in centimetres; the calculator converts it before multiplying.
How much extra ready-mix should I order?
Simple measured pours often use 5–10%, but forms, grade, access, and supplier increments can change the appropriate allowance.
Does the result include reinforcement?
No. Rebar, mesh, fibers, forms, and base material are separate planning items.