Pedestal Calculator

Pedestal calculator: one support at every paver corner

A pedestal calculator counts the supports you need under a paver deck. Put one pedestal at every corner where four pavers meet. The count is (columns + 1) × (rows + 1). A 20 × 12 ft deck with 24 × 24 in pavers has 10 columns and 6 rows of pavers, so it needs 11 × 7 = 77 pedestals.

What a pedestal does

A deck pedestal is a small adjustable post that holds a paver above the roof membrane. Water runs under the paver and off the deck.

Picture a sheet of graph paper. Each paver is one square. Each pedestal is one dot where two lines cross. Count the dots, and you have the pedestals.

The pedestal formula

1. Columns = deck length ÷ paver length, rounded up to a whole paver.
2. Rows = deck width ÷ paver width, rounded up to a whole paver.
3. Pedestals = (columns + 1) × (rows + 1).
4. Interior pedestals = (columns − 1) × (rows − 1). These are the dots not on the deck edge.
5. Perimeter pedestals = total pedestals − interior pedestals.
6. Pavers = columns × rows.

Rounding up matters. A 20 ft run with 2 ft pavers is exactly 10 pavers. A 20.5 ft run needs 11, because the last paver has to cover the extra half foot.

Worked examples

These match the calculator exactly.

Example 1: a 20 × 12 ft roof deck with 24 × 24 in pavers.

• Columns: 20 ÷ 2 = 10
• Rows: 12 ÷ 2 = 6
• Pedestals: 11 × 7 = 77
• Interior: 9 × 5 = 45
• Perimeter: 77 − 45 = 32
• Pavers: 10 × 6 = 60

Example 2: a 16 × 10 ft deck with 24 × 48 in pavers, the 48 in side running along the 16 ft length.

• Columns: 16 ÷ 4 = 4
• Rows: 10 ÷ 2 = 5
• Pedestals: 5 × 6 = 30
• Interior: 3 × 4 = 12
• Perimeter: 30 − 12 = 18
• Pavers: 4 × 5 = 20

Reference table: a 20 × 12 ft deck by paver size

Paver size	Columns × rows	Pedestals	Perimeter	Interior	Pavers
24 × 24 in	10 × 6	77	32	45	60
18 × 18 in	14 × 8	135	44	91	112
16 × 16 in	15 × 9	160	48	112	135
24 × 48 in	5 × 6	42	22	20	30

The 24 × 48 row runs the 48 in side along the 20 ft length, so it has 5 columns and 6 rows.

Edge pedestals and cut pavers

The perimeter pedestals sit at the deck edge, where the paver grid stops. Edge pavers are often cut to fit, so the pedestal under a cut paver may need to sit closer to the edge. Many installers use a half-tab or a pedestal with a wider base at the edge. Plan for a few extra edge pedestals, and check the pedestal’s bearing area on a cut.

How to measure

• Measure the deck length and width at the finished deck surface, not the frame.
• Measure one paver to get its exact size. Nominal sizes can differ by a few millimetres.
• If the deck has a curb, a planter, or a corner cut-out, count those pavers separately.
• Check the membrane and drain slope before you place the first pedestal.

Common mistakes

• Counting pedestals as one per paver. Pedestals sit at the corners, so there are more of them than pavers.
• Forgetting the extra row and column. The +1 is the edge line that closes the grid.
• Mixing up the 24 × 48 orientation. Put the long side on the length you measured, or the grid will be wrong.
• Skipping the span check on large pavers. A 24 × 48 in paver can need a mid-span support, so confirm with the manufacturer.

Related calculators

Pedestal decks start with the surface you are covering. The paver calculator gives the paver count for a ground-level patio, and the paver base calculator sizes the base under a ground patio. If the deck is wood or composite, the composite decking calculator covers the boards.