Concrete & Post Hole Calculator
How many bags do you need? Enter your project dimensions below — we'll do the math in real time.
Typical: 10" for fence posts, 12"–16" for deck posts
Rule of thumb: bury ⅓ of post height + 6" (frost line in Portland is ~18")
Bags typically come in 40 lb, 60 lb, and 80 lb sizes. 60 lb is easier to mix by hand; 80 lb is more economical for large pours. We stock both at all three locations — check store hours →
Quick Tips
Post Depth Rule of Thumb
For fence posts: bury ⅓ of the total post length. For a 6-ft fence, use 9-ft posts buried 3 ft deep. Portland's frost depth is ~18" — posts holding structure should be deeper.
Fast-Set vs. Regular Mix
Fast-set concrete (Quikrete Fast-Setting, SAKRETE Fast-Setting) sets in 20–40 minutes and can be dry-poured directly into the hole without mixing first. Regular mix takes 24–48 hours but is stronger for structural applications.
Slab Thickness Guide
Foot traffic only: 3.5"–4". Car traffic / driveway: 5"–6". Machinery or heavy loads: 6"+. Always compact and level the sub-base before pouring.
When to Call for Concrete
If your slab calculation exceeds ~50 cubic feet (about 2 cubic yards), it's often cheaper and faster to order ready-mix from a local batch plant rather than mixing bags. Ask our staff for local ready-mix contacts.
Come in to any of our three locations — our staff will help you figure out exactly what you need. We stock Quikrete, SAKRETE, and other concrete mixes at all locations.