Calculators → Concrete
Post Hole Concrete Calculator
Tell us your project — we recommend spacing, depth, post size & cure time
Enter total run length — we'll recommend the rest
Rule: 3× post width
Min 36" in cold climates
US avg: ~$6.98
US avg: ~$9.48
US avg: ~$11.98
Update with today's actual temp
Includes 10% waste · Store trips = 10 bags per car load
Frost Depth by City (Canada & US)
Post holes must extend below the frost line to prevent heaving. Use the calculator above for your exact region. These are minimum recommended depths.
| City | Region | Frost Depth | Min Post Hole |
|---|---|---|---|
| Vancouver, BC | Canada | 12" | 18" |
| Calgary, AB | Canada | 48" | 54" |
| Edmonton, AB | Canada | 60" | 66" |
| Winnipeg, MB | Canada | 72" | 78" |
| Toronto, ON | Canada | 48" | 54" |
| Ottawa, ON | Canada | 60" | 66" |
| Montreal, QC | Canada | 60" | 66" |
| Quebec City, QC | Canada | 72" | 78" |
| Halifax, NS | Canada | 48" | 54" |
| Miami, FL | US | 0" | 12" |
| Atlanta, GA | US | 6" | 12" |
| Dallas, TX | US | 10" | 18" |
| Los Angeles, CA | US | 0" | 12" |
| Phoenix, AZ | US | 0" | 12" |
| Denver, CO | US | 36" | 42" |
| Chicago, IL | US | 42" | 48" |
| Detroit, MI | US | 42" | 48" |
| Minneapolis, MN | US | 60" | 66" |
| Seattle, WA | US | 12" | 18" |
| New York, NY | US | 36" | 42" |
| Boston, MA | US | 48" | 54" |
| Philadelphia, PA | US | 36" | 42" |
| Portland, OR | US | 12" | 18" |
| Salt Lake City, UT | US | 30" | 36" |
| Anchorage, AK | US | 72"+ | 84" |
Post Hole Depth Guide by Post Height
General rule: bury 1/3 of total post length plus extend below frost line. These are minimums for standard fence posts in average soil.
| Post Height (above ground) | Total Post Length | Min Hole Depth | Recommended Dia. |
|---|---|---|---|
| 4 ft fence | 6 ft | 24" | 8-10" |
| 5 ft fence | 7-8 ft | 28-30" | 10" |
| 6 ft fence | 8-9 ft | 30-36" | 10-12" |
| 8 ft fence | 10-11 ft | 36-42" | 12" |
| Deck post (8 ft) | 10 ft | 36-42" | 12" |
| Deck post (12 ft) | 14 ft | 42-48" | 12-16" |
| Mailbox post | 6 ft | 18-24" | 8" |
| Light pole (10 ft) | 12 ft | 36-42" | 12" |
Concrete Bags per Post Hole
Quick reference for common post hole sizes. Use 80 lb bags for best value on larger holes.
| Hole Size | Depth | 40 lb Bags | 60 lb Bags | 80 lb Bags |
|---|---|---|---|---|
| 8" dia | 24" | 3 | 2 | 2 |
| 8" dia | 36" | 4 | 3 | 2 |
| 10" dia | 24" | 4 | 3 | 2 |
| 10" dia | 36" | 6 | 4 | 3 |
| 10" dia | 48" | 8 | 6 | 4 |
| 12" dia | 36" | 9 | 6 | 5 |
| 12" dia | 48" | 12 | 8 | 6 |
| 12" dia | 60" | 15 | 10 | 8 |
Always verify frost depth with your local building department. Depths shown include 6 inch clearance below frost line.