SettingsSettings for this calculationUS
The diameter of the drilled cylindrical foundation.
Match the diameter to the sign post's structural design and the auger size used for drilling.
How deep the foundation is drilled below grade.
Depth depends on soil conditions, frost depth, and the sign's exposed height and wind loading — confirm against the project's structural drawings.
Foundation concrete volume
0.08367 yd³
They open the calculator with your figures already in it
Traffic Sign Post Foundation Concrete Calculator: 0.0837 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)
- Foundation volume = π × (foundation diameter ÷ 2)² × foundation depth, standard cylindrical footing volume applied to a drilled sign post foundation
Inputs used
- Foundation Diameter
- 0.98 ft
- Foundation Depth
- 3 ft
What this calculation does not cover
- Alongside a road, a sign foundation is a safety item before it is a concrete item. Posts inside the clear zone are required to break away or yield on impact, which puts rules on how far the foundation may finish above grade and on the slip base or frangible coupling that sits on top of it. A rigid post grouted into a plug standing proud of the ground is a fixed hazard regardless of how correct its volume is.
- The cylinder includes the space the post occupies. A 100 mm (4 in) post through a 300 mm (12 in) hole displaces roughly a tenth of the concrete shown, which quietly cancels part of any allowance added for an oversized auger cut — worth knowing when one truck is servicing a run of foundations that are each a fraction of a cubic metre.
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 2026-09-06 · in the site-wide review of 2026-09-06 · v1.0.1
Regulatory standards & verification citations1
- Foundation volume = π × (foundation diameter ÷ 2)² × foundation depth, standard cylindrical footing volume applied to a drilled sign post foundation
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.
Tools and safety for this job
To place and finish concrete and set fence posts. Generic types, no brands, no prices.
Protection this work requires
- Wet cement and lime burn skin and eyes painlessly until the damage is done: waterproof gloves to EN 374, safety glasses whenever the mix can splash, and never kneel in wet mix in permeable trousers.
- Boards, blocks and bagged material cause most lasting back injuries on small sites: two people or a lifter for full sheets, and never a bag on one shoulder up a ladder.
- Digging blind strikes gas, water and power every day: get the plans, scan with a cable avoidance tool, and hand-dig trial holes over anything you find.
Show the 13 tools this job needsHide tools
Essential
Bull float and edger
Cable and pipe detector
Mixing bucket or tub
Post hole digger or auger
Screed bar or rail
Shovel and spade
Spirit level
String line and pins
Tape measure
Wheelbarrow
Recommended
Plate compactor
Post driver
Optional
Power float
what each concrete tool is for and what each landscaping tool is for, and the spec that decides which to buy where one does.