Basement cost = excavation + concrete walls and slab + waterproofing + finishing, each priced by quantity. A 10 × 8 m basement 3 m deep with 250 mm walls needs about 325 m³ of digging, 38 m³ of concrete and 188 m² of waterproofing, and gives 71 m² of usable floor. At the example rates that is about 44,600, or 625 per m² of usable floor.
My Construction Calculator
Basement Construction Cost Calculator
Inputs
Results update as you type.
Diagram updates as you type.
Results
Check the working before you order.
Estimated basement cost
44,566
Excavation (324.58 m³)
4,869
Concrete (38.25 m³)
9,563
Waterproofing (188.0 m²)
3,760
Interior finishing (71.3 m²)
21,375
Other items
5,000
Usable floor area inside the walls
71.3 m²
Cost per m² of usable floor
625
Concrete: walls + slab
26.25 + 12.00 m³
Excavation (bank volume)
324.6 m³
Budget estimate from your rates. Ground water, rock, shoring and design fees can add a lot: get a site survey and quotes.
Price This optional: add your own prices
Your prices are remembered on this device only.
Send Order WhatsApp, SMS or email to your supplier
Waterproofing = outside of the walls + floor = 2(L + W) × depth + L × W = 188.0 m²
Excavation: 324.58 m³ × 15.00 = 4,869
Concrete: 38.25 m³ × 250.00 = 9,563
Waterproofing: 188.00 m² × 20.00 = 3,760
Interior finishing: 71.25 m² × 300.00 = 21,375
Total = 39,566 + other 5,000 = 44,566
Scan to open this calculationThe code links to this calculator with your inputs, so anyone can scan it with a phone camera and see the same result. Save it for a report, a site board or WhatsApp.Test copy: this code opens the live site, myconstructioncalculator.com, so it works on a phone once the site is launched.
Results are estimates for planning and material ordering only. They are not a substitute for structural design or approval by a qualified engineer. Read the full disclaimer.
Quantities for Common Sizes (3 m deep, 250 mm walls)
Outside size
Excavation
Concrete
Waterproofing
Usable floor
8 × 6 m
209 m³
27.5 m³
132 m²
41.3 m²
10 × 8 m
325 m³
38.3 m³
188 m²
71.3 m²
12 × 10 m
466 m³
50.3 m³
252 m²
109.3 m²
Frequently Asked Questions
How do I estimate the cost to build a basement?
Work out the quantities first (excavation, concrete for walls and floor, waterproofing and finishing area), then multiply each by a local rate. Quantities come from the size and depth; rates come from local contractors.
Why is the excavation bigger than the basement?
Builders dig a working space around the walls, usually 0.6 m (2 ft), to set up formwork and apply waterproofing. The digging also goes down to the bottom of the floor slab.
What makes a basement cost more?
Ground water, rock, a tight site that needs shoring, and deep basements. These can add more than the concrete itself, so a site survey comes first.
How much waterproofing does a basement need?
Cover the outside of the walls below ground and the floor: 2 × (length + width) × depth + length × width. A 10 × 8 m basement 3 m deep needs 188 m².
How is the cost per square foot worked out?
Total cost divided by the usable floor area inside the walls. Thick walls reduce the usable area, so the cost per m² or ft² is higher than for the same footprint above ground.
Embed This Calculator on Your Website
Free for any website: contractors, suppliers, blogs and schools. Paste this code where you want the calculator to appear. It works in WordPress (Custom HTML block), Wix, Squarespace and plain HTML.
