Build a hole schedule and a product-yield record before estimating bags. The post-concrete calculator converts that record into volume and whole bags; it does not choose hole dimensions, embedment or a concrete product.
Group holes by matching profiles
Record the number of circular holes with the same diameter, total depth and gravel depth. If dimensions vary, retain separate groups and estimates. The cylindrical model does not describe tapered or rectangular excavations.
| Field observation | Record for the calculator |
|---|---|
| Hole width | Diameter across the circular hole, not post diameter. |
| Total hole depth | Full depth, with gravel depth recorded separately. |
| Post occupying the concrete | Round diameter or actual rectangular width and depth; note whether displacement is enabled. |
| Different hole/post profile | A separate group instead of one representative profile for every post. |
Hole and embedment requirements must come from the project information, local requirements and selected product instructions. Measure finished holes at representative locations and retain uncertainty about excavation shape and site handling when selecting the waste allowance.
Copy yield from the bag you intend to buy
Keep product name, bag size and stated volume yield together. A weight such as 60 pounds is not itself a volume yield. Enter the label's cubic feet per bag in US mode or litres per bag in metric mode; do not copy a different product's value.
Read per-post volume and the combined purchase differently
For the existing example of four 10-inch-diameter holes with 30 inches of concrete depth and no modeled post displacement, one hole holds about 1.36 ft³. Together they require about 5.45 ft³ before waste. With a user-selected 10% allowance and the example product yield of 0.45 ft³ per bag, the combined order is 14 bags.
That is a project bag count, not a direction to round each hole to four bags. The calculator pools volume across the entered matching holes and rounds only the final purchase. Substitute your actual product yield and measurements before ordering.
The post-hole reference CSV is a separate fixed-profile comparison: one hole, 12-inch diameter and 0.45 ft³ bag yield. Keep those assumptions attached when using it to compare depths.
Retain a checkable record
- Keep gravel depth outside the concrete-filled depth.
- When subtracting a post, use its dimensions only through the concrete-filled depth.
- Keep the exact product-yield record with the rounded bag quantity.
- Retain net volume and selected waste separately so substitutions can be rechecked.
- Record price after the quantity assumptions are settled.
For equations and numerical boundary rules, use the concrete methodology. The measurement guide explains accepted dimension formats.
Limits and sources
The QUIKRETE Fast-Setting Concrete Mix data sheet is a manufacturer example: it lists approximate yields of 0.375 cubic foot for its 50-pound bag and 0.45 cubic foot for its 60-pound bag. Those values are not universal and may change, so check the product being purchased. Exact unit conversions use the NIST SP 811 conversion factors. The concrete methodology documents MaterialNest's volume, displacement, waste, and rounding sequence.
Soil capacity, frost depth, wind exposure, post loading, drainage, hole geometry, and local rules are outside this estimate. Have critical footing and structural decisions reviewed by an appropriate qualified professional.
Send product-yield or formula corrections to feedback@materialnest.com.