HesapHanem

Retaining Wall Block Calculator

Find how many wall blocks.

How it is calculated

The wall length and height are entered in metres and the block face in centimetres. The tool computes the wall area A = length × height in m² and the area of one block face a = (block length ÷ 100) × (block height ÷ 100) in m². The count is blocks = ceil(A ÷ a × 1.05): the plain division, plus a fixed 5% allowance for cuts and breakage, always rounded up to a whole block. Block thickness (depth) is not asked for, because only the visible face matters for a single-width wall. Mortar joints, a coping or cap course, buried base courses and a second block row for a thicker wall are not included. Both wall sizes may be 0 (the result is then 0); the block sizes must be above zero.

Worked example

A wall 6 m long and 1.2 m high, built from blocks that show a face of 40 cm × 20 cm. Wall area = 6 × 1.2 = 7.2 m². One block face = 0.40 × 0.20 = 0.08 m². Blocks without waste = 7.2 ÷ 0.08 = 90. Adding 5% gives 90 × 1.05 = 94.5, which rounds up to 95 blocks. If you also bury one base course under the ground, add those blocks separately: they are not in this count.

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Common mistakes

  • Entering the wall in centimetres or the block in metres. The wall fields are metres and the block fields centimetres; typing 0.4 for a block turns it into a 0.4 cm block and the count explodes (about 9,450 for the example wall).
  • Entering the thickness of the block as its height. Only the visible face is used (length and height on the wall); the depth going into the hill is never asked for.
  • Using the block's nominal size while laying with thick mortar joints. If joints add 1 cm each way, enter 41 × 21 so the count matches the real coverage.
  • Forgetting the buried base course and the cap. The tool counts the visible wall area only, so add base and cap blocks yourself.
  • Treating 5% as enough for a wall full of corners, curves and steps. Each cut wastes part of a block, so a complex layout needs more than the tool's allowance.

About this calculator

This calculator finds how many retaining wall blocks a project needs by dividing the wall's total face area (length × height) by the face area of a single block, then adding a margin for cuts and waste.

Landscapers and hardscape contractors use it to quote jobs and order pallets of block in the right quantity, and homeowners use it to budget a DIY retaining wall or garden edging project before heading to the yard.

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  • Editorial team

    Blocks arrive on pallets, so turn the count into an order: if a pallet holds 40 blocks, the 95 blocks of a 6 m by 1.2 m wall of 40 by 20 cm faces means 3 pallets, since 2.4 rounds up. Ask your supplier for the real pallet quantity and whether caps are sold separately. This tool covers the visible face only, so a taller or curved wall is worth a word with a local installer. What block size are you building with?

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