Zerdly

Bench Height Checker

Computes the bench-height-to-burden stiffness ratio H/B with a sweep table, and compares it with a reference range only if you supply one and its source — no built-in safe or stiff verdicts.

100% FreeRuns in your browserBasic
How to use this calculator

Inputs

Stiffness ratio H/B from bench height and burden, with a sweep table and an optional comparison against YOUR sourced reference range.

Bench

Crest to toe of the bench — not the drilled hole length (that adds subdrill).

More options
Hole (for the diagram)

Shows the drilled length of a vertical hole. It does not change H ÷ B.

Compare with your reference range
H/B
H/B
Compare another design

Enter the values and press Calculate.

Or load an example to see a worked result.

Bench geometry and charge basis
Not to scale
Bench geometry and charge basisSection through a blast bench: crest, free face and toe, a blast hole set back by the burden, bench height from crest to toe, and subdrill below the toe.HoleCrestToeFreefaceHBSubdrillHole length ≠ H
Bench height H (not entered), measured crest to toe. Burden B (not entered) from the hole to the free face. A drilled hole usually continues below the toe (subdrill), so hole length is longer than bench height.

Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.

How to use this calculator

  1. Enter the bench height (crest to toe) and the burden.
  2. Optionally add the subdrill to see the drilled hole length, and a reference ratio range from your blast design with its source.
  3. Read the ratio, the sweep table across burdens and — only if you entered a range — whether the ratio is below, within or above it.

How it works

Stiffness ratio = bench height ÷ burden (H/B). It has no units, so any consistent length unit gives the same value, and scaling both by the same factor leaves it unchanged.

Bench height is not hole length: a drilled hole usually continues below the toe (subdrill), so it is longer than H. The ratio uses H.

The tool gives no safe, stiff or well-proportioned verdict of its own. With your range it reports Below, Within or Above (inclusive at both ends) and names your source.

Worked example

10 m bench, 3 m burden. H/B = 10 ÷ 3 = 3.33. With 1 m of subdrill a vertical hole is 11 m long, but the ratio still uses 10 m. Against a design range of 2 to 3 it reads Above your range; with no range entered there is no verdict.

Frequently asked questions

Bench or hole height?

Bench height — crest to toe. The drilled length adds subdrill (and is longer again for an angled hole), so using it would overstate the ratio.

Does ratio prove good design?

No. H/B alone cannot assess stability, fragmentation, airblast, flyrock or safety. It is one geometric quantity to compare with your approved blast design.

Where do reference ranges come from?

From your site blast design, standard or engineer — enter the range and record its source. The tool does not supply a range because none applies universally.

Related tools

Explore more in Mining, Quarry, Earthworks, Drill & Blast.

Cite this tool

Zerdly. (2026). Bench Height Checker. Retrieved from https://www.zerdly.com/tools/bench-height-checker/

Tip: Enter any known values to calculate the remaining results.

Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.