Concrete slab
Measure rectangular areas and add them together.
Concrete Calculators
Calculate concrete slab and post-hole volume, then convert your required volume to bags using a product yield you can verify.
Post-hole volume
Subtract the post from the hole volume.
Concrete bags
Turn volume and product yield into bag counts.
Choose your project
Start with the job you are measuring. Keep its dimensions and assumptions together.
Concrete for a Patio Slab
Estimate a rectangular patio pour with a visible measurement diagram, chosen allowance and product-specific bag conversion.
Concrete Quantity for a Shed Base
Calculate the concrete volume for a specified shed-base footprint without treating the example depth as a construction recommendation.
Concrete for Separate Path Sections
Estimate concrete for separate path rectangles with different widths, keeping gaps and overlaps out of the total.
Combine Quantities for Multiple Slabs
Combine compatible slab quantities before whole-bag rounding, or keep separate purchases explicit when the project needs them.
Concrete for Multiple Post Holes
Plan concrete for groups of post holes with different dimensions, subtract round posts and combine unrounded material requirements.
Concrete Bag Yield: Weight, Mixed Volume and Bag Count
Use a concrete bag’s stated mixed yield to calculate whole bags. See manufacturer-specific yield examples, a checked 1 cubic yard calculation and common unit mistakes.
A volume estimate starts with your measurements
Follow each quantity from the measured space to the amount you order.
Measurements
Measure each section and choose its units. Keep separate areas and openings explicit.
Net volume
Calculate the measured volume first. Subtract any supported displacement before adding an allowance.
Your allowance
Enter an allowance that suits your job. See it separately from the net quantity.
Packs or bulk
Use your product's yield or capacity. Round up whole packs only after the required quantity is known.
Make sense of the numbers
Bags or Bulk: Compare Quantities Before You Buy
Compare bagged and bulk material quantities without assuming prices, delivery terms, package capacities or a universal density.
Read the guideHow Rectangular Volume Is Calculated
Understand rectangular material volume, mixed-unit conversion and multi-section totals with a formula you can check.
Read the guideRead the complete category guide, questions and sources
Choose a shape first
A slab is calculated from length, width and depth. A cylindrical hole uses its radius and depth; a post occupying part of the hole is deducted. For a project with several areas, keep each set of dimensions so the total remains easy to check.
Separate volume from bag yield
The size of a hole or slab tells you its volume. It does not tell you how much mixed concrete a particular bag will produce. Enter the yield from your selected product when you want a bag count.
Use your chosen specification
PackLedge calculates quantities from dimensions you supply. It does not select slab thickness, hole depth, reinforcement or structural capacity. A worked patio or shed-base example explains the arithmetic, not a construction specification.
Sources and method
- PackLedge quantity methods
Original derivations using geometry, ratios, sums and whole-package rounding. Each calculator explains its assumptions and worked examples.
- Your selected product label or technical sheet
The source for the coverage, mixed yield, density, package capacity, sheet dimensions or wallpaper repeat that you enter.