Footings
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Custom Concrete Volume Calculator – Work Out Your Pour Before You Order
How do you work out how much concrete you need? Use the Custom Concrete calculator to get a clear, reliable figure for your footings, slab, or patio in seconds. No need for mental arithmetics – you simply enter your length, width, and depth to establish your baseline cubic meterage straight away.
Custom Concrete has spent two decades refining on-site delivery using a state-of-the-art fleet of volumetric mixing trucks. That means our calculator gives us your target baseline, but our drivers calibrate and batch the mix right on your site, guaranteeing you never pay for unused concrete.
Use the calculator to get your baseline estimate, then check our trade guide below on factoring in excavation waste and irregular ground.
Useful Volume Adjustments – Accounting for Ground Absorption & Slump
Taking the raw number from the Custom Concrete calculator gives you a reliable starting point, but soil porosity, trench wall integrity, and sub-base texture can all eat into your total volume. If you apply a quick percentage adjustment to your baseline figure you’re guaranteed not to be caught short with half a slab unpoured.
- Smooth Formwork / Rigid Shuttering – Add 5% extra to compensate for slight variations in sub-grade level across the slab footprint.
- Raw Earth Footings & Clay Trenches – Add 10% to 12% extra to account for trench wall blowouts, soft spots, and side absorption.
- MOT Type 1 / Open Sub-Bases – Add 5% to 8% extra as wet concrete seeps into the top layer of compacted stone.
Tackling Irregular Pours – L-Shapes, Slopes, and Circular Bases
Combining your baseline figure with a ground waste factor works cleanly for standard rectangular slabs. But your site may involve wrapped corners, post footings, or sloping ground. Rather than starting to work out equations on paper, you can split complex footprints into simple zones – and then let our calculator handle the maths for you.
- L-Shaped & Wrap-Around Patios – Draw an imaginary line down the corner join to split the pour into two simple rectangles. Calculate each zone separately in the tool above, then sum the total cubic metres.
- Circular Bases & Post Footings – Select the circular post base option directly in the Custom Concrete calculator. Enter your hole diameter and depth to get an instant volume figure per hole, then multiply by your total post count.
- Sloped Sub-Bases & Ramp Footings – Measure your excavation depth at the shallow end and the deep end, then divide by two to get your true average depth. Using this average stops you over-ordering on high ground or running short at the drop.
Quick Sanity-Check
Did you convert your depth to metres?
Site plans and measuring tapes usually use millimetres, but concrete volume is measured in cubic metres. Misplacing a decimal point in the depth field will give you a wildly inaccurate figure or panic when reviewing your quote.
Before entering your dimensions into the Custom Concrete calculator, double-check that your depth figure is expressed as a fraction of a metre:
- 100mm (Standard Shed Base / Patio): Divide by 1,000 – 0.1m
- 150mm (Light Vehicle Driveway): Divide by 1,000 – 0.15m
- 225mm (Heavy Commercial Slab): Divide by 1,000 – 0.225m
- 300mm (Trench Footing Depth): Divide by 1,000 – 0.3m
The Volumetric Safety Net – No Waste, No Part-Load Penalties
No matter how careful you are when calculating the volume of concrete you need, your site can deliver unwelcome surprises. Which is where volumetric delivery provides you with a safety-net.
Custom Concrete operates a state-of-the-art fleet of mobile volumetric mixers that batch raw aggregates, water, and cement directly on your site, turning your calculator figure into a risk-free target.
- Pay Only for What Hits the Ground – Digital flow meters measure output in real time. If your trench takes 2.3m³ instead of your estimated 2.5m³, you are billed strictly for 2.3m³.
- No Part-Load Surcharges – Standard barrel trucks hit you with heavy penalty fees for carrying partial loads. Volumetric trucks haul raw materials in bulk, eradicating part-load charges entirely.
- On-Site Slump & Mix Adjustments – Need a slightly wetter slump for a narrow trench or a stronger mix mid-pour? Drivers adjust the water-to-cement ratio right from the truck control panel.
- Guaranteed Fresh Concrete – Because we mix your concrete fresh, exactly where you need it, you get maximum working time to lay and finish the slab.
Site Prep, Delivery & Curing – Custom Concrete FAQs
Light drizzle won’t damage a fresh slab once it is placed, but heavy rain before the initial set (usually the first 1 to 2 hours) washes the cement binder off the top, leaving a weak, dusty surface. Keep heavy-gauge polythene sheeting on site to throw over the fresh pour if you get a downpour.
Our volumetric trucks feature a rear-mounted hydraulic chute that extends up to 4 metres directly from the rear bumper. If your pour site is further back, across soft ground, or behind a narrow side alley, we can provide concrete pump hire of either a ground line pump or boom pump to transport the wet concrete.
Our trucks are 10 metres long, 2.5 metres wide and 4 metres high. Fully loaded, the truck weighs up to 32 tonnes, so ground surfaces and access driveways must be capable of supporting heavy commercial axles.
Because our volumetric trucks batch raw materials directly on site, there is no minimum volume restriction or part-load waste penalty. Whether your trench takes 0.5m³ or 8m³, you only pay for the exact quantity discharged into your dig.
Ready to Pour? Schedule Your Volumetric Concrete Order Today
Once you have run your dimensions through the Custom Concrete calculator, give our team a call. We will run through your access route, confirm your mix specification, and dispatch one of our state-of-the-art volumetric mixers directly to your site. You get fresh batching at the chute, complete volume control, and no wasted material.
Call our site specialists today on 01525 861899 to schedule your pour.