SettingsSettings for this calculationUS
Waste is set to 5% by hand. Pick a tier above to replace it, or keep your own figure.
The overall outside length of the pit or basin.
Measure the full outer footprint, including walls.
The overall outside width of the pit or basin.
Measure perpendicular to the length.
The overall outside height (depth) of the pit or basin.
Includes the base slab thickness.
The thickness of the concrete walls and base.
Assumed uniform on all sides and the base.
Extra concrete for spillage.
5% is standard for this kind of pour.
Concrete volume needed
1.13 yd³
Assumes a simple open-top rectangular box with uniform wall and base thickness — real sump designs often have a sloped or stepped base for pump clearance.
- Outer block volume
- 2.07 yd³
- Interior void volume
- 1 yd³
- Base volume (no waste)
- 1.07 yd³
They open the calculator with your figures already in it
Sump Pit & Catch Basin Concrete Calculator: 1.13 yd³ — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Show calculation logicHide calculation logic
How this was calculated
Formula source(s)
- Concrete volume = outer block volume minus the hollow interior void (an open-top box with walls and a base of uniform thickness)
Inputs used
- Outer Length
- 4 ft
- Outer Width
- 4 ft
- Outer Height
- 3.5 ft
- Wall & Base Thickness
- 6 in
- Waste Factor (%)
- 5
Intermediate steps
- Outer block volume
- 2.07 yd³
- Interior void volume
- 1 yd³
- Base volume (no waste)
- 1.07 yd³
Confidence note: Assumes a simple open-top rectangular box with uniform wall and base thickness — real sump designs often have a sloped or stepped base for pump clearance.
What this calculation does not cover
- The shape is a plain rectangular box with one thickness for the walls and the base. It adds nothing for a sloped or stepped base under the pump, benching or a flow channel through a catch basin, a haunch at the wall-to-base joint, or walls that thicken toward the bottom.
- No openings are deducted and no cover is added. Pipe penetrations, inlet and outlet knockouts and a grate or frame recess all come off the real pour, while a lid, cover slab or ladder rebate all go on it — neither adjustment is in this number.
- Reinforcement, formwork and waterproofing sit outside the estimate. No rebar, mesh, dowels or lifting anchors are counted, their displaced volume is not taken off the concrete, and there is no allowance for blinding under the base, tanking, or concrete lost into over-break where a wall is poured against soil instead of a form.
- This is a quantity, not a structural design. It does not check the thickness you entered against soil and groundwater pressure on the walls, against wheel or buffer loads on the base, or against uplift on an empty pit in a high water table. Those calls set the thickness; this only prices the thickness you were given.
- It does not size the pit. The interior void it reports is raw geometry, not usable storage between pump float levels, and it takes no view on how much sump depth to leave below the outlet for sediment in a catch basin.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-02 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- Concrete volume = outer block volume minus the hollow interior void (an open-top box with walls and a base of uniform thickness)
Cite this page
Your workspace
Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.