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.
How this tool differs: This broad calculator handles slab-like pads and floors as well as paths, walls, trenches, and other rectangular pours. Enter the finished slab thickness as depth; Concrete Bag converts volume to retail premix bags, while 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.
See the concrete estimate in context.
Small equipment pad
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)
The extra 0.15 yd³ provides a modest field allowance, but the supplier may require rounding to its delivery increment.
Metric garden path section
Length 5 m; width 3 m; depth 12 cm; waste 5%
Working: 5 × 3 × 0.12 × 1.05
Result: 1.89 m³ to order
This covers one constant-depth rectangle; curves or changing depths should be split into measured sections.
Turn the number 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.
Assumptions
- 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 pours 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 does not decide.
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.