Reinforced Slab Calculator
Work out the concrete volume, approximate weight and mesh reinforcement needed for a standard reinforced slab on ground.
Reinforced Slab Calculator
Work out concrete volume and mesh reinforcement for a standard slab on ground.
Estimating Concrete And Reinforcement For A Slab On Ground
Not every reinforced slab fits neatly into a "waffle" or "raft" category — sheds, garages, extensions and smaller structures are often built as a straightforward reinforced slab on ground. This calculator focuses purely on the quantities involved: concrete volume, approximate weight, and how many standard mesh sheets are needed to reinforce the slab.
Concrete volume is calculated as area (m²) × thickness (m). A recommended order volume adds 5 per cent to cover minor formwork loss and site variation, and the approximate weight is calculated using standard concrete density of 2.4 tonnes per cubic metre. Mesh sheets are estimated by dividing your slab area by 13.5 square metres — a standard 6 m × 2.4 m (14.4 m²) sheet allowing for typical side and end laps.
What Information You Need To Enter
Enter your slab area in square metres and select a thickness between 100 mm and 200 mm. Most residential slabs for sheds, garages and patios fall within this range, though your engineer may specify a different thickness for structural or loading reasons.
Understanding Your Results
The calculator returns concrete volume required, a recommended order volume with a 5 per cent allowance, the approximate weight in tonnes, and the number of standard mesh sheets needed. These figures are designed for planning and ordering purposes — your final reinforcement layout should always follow engineering drawings where structural certification is required.
Why Accurate Estimating Matters
Ordering concrete and mesh accurately reduces waste, avoids a second delivery mid-pour, and helps you budget a smaller slab project without needing a full engineering quote just to get a ballpark figure.
Frequently Asked Questions
What is a reinforced slab on ground?
It is a concrete slab poured directly on a prepared and compacted base, reinforced with steel mesh, commonly used for garages, sheds, patios and smaller residential structures.
How much mesh overlap should I allow for?
Standard practice is a minimum lap of around 225 mm on the sides and 300 mm at the ends of adjoining sheets, which is why this calculator uses an effective coverage of 13.5 m² per 14.4 m² sheet.
What thickness slab do I need?
This depends on the intended use and any vehicle loading. A shed or patio slab is often 100 mm, while a garage or driveway slab exposed to vehicle weight typically needs 150 mm or more. Always confirm with your engineer or building surveyor.
Does this calculator include site preparation or excavation?
No -- this calculator focuses on concrete and mesh quantities only. Use the Excavation Calculator or Crushed Rock Calculator for base preparation quantities.
Can I get a fixed price for a reinforced slab?
Yes. Once you know roughly what your project involves, request a free quote and we will assess your site and provide an accurate, fixed price.
Related Calculators & Services
Need An Exact Price, Not Just An Estimate?
The Reinforced Slab Calculator gives you a fast, useful planning figure. For a fixed, accurate price backed by a site assessment, request a free professional quotation from HPL Construction.
