Pier Block Count Calculator
Count the precast pier blocks for a deck or shed floor from its size and the spacing between piers along and across the beams.
How it works
piers per beam = floor(length ÷ pier spacing) + 1 · beam lines = floor(width ÷ beam spacing) + 1 · total = piers per beam × beam lines
Pier blocks sit in a grid: one row of piers under each beam, spaced along the beam’s length. Along any line, the number of supports is the span divided by the spacing, rounded down, plus one for the end post — a 12-foot beam at 6-foot spacing needs supports at 0, 6 and 12 feet, so three. Multiply piers per beam by the number of beam lines for the total. This is for on-grade or floating structures; frost-depth footings are a different, poured detail.
Worked example
A 12 × 10 ft frame with piers every 6 ft along beams set 6 ft apart: floor(12 ÷ 6) + 1 = 3 piers per beam, and floor(10 ÷ 6) + 1 = 2 beam lines, so 3 × 2 = 6 pier blocks.
Frequently asked questions
When can I use pier blocks instead of poured footings?
Precast pier blocks suit floating decks, sheds and ground-level platforms that are not attached to a house. Anything attached to the home, or in a frost-heave climate, generally needs footings poured below the frost line instead.
How far apart can pier blocks be?
Spacing depends on the beam and joist size and the load, but 4–8 feet is typical, with 6 feet a common default. Closer spacing lets you use smaller beams; a span table matches the two.
Do pier blocks need a base?
Set each block on a few inches of compacted gravel so it drains and does not settle unevenly. Level the tops to each other — shims or adjustable post bases handle the final fine-tuning.
Related calculators
Estimates only — add for waste and confirm against local building codes and supplier specs.