Sample Spacing Calculator
The tool models a regular square sampling grid over a plan area A.
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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
- Enter the sample area in m², or enter the strike length and width and the tool multiplies them into an area.
- Enter EITHER a target number of samples (to get the recommended square-grid spacing) OR a grid spacing in metres (to estimate how many samples that grid needs) — not both.
- Read the grid spacing, sample count and samples-per-hectare density, then adjust to suit geology and QA/QC requirements.
How it works
The tool models a regular square sampling grid over a plan area A. For a target sample count n the nominal spacing is s = √(A ÷ n); conversely a chosen spacing s covers roughly n = A ÷ s² sample points. Area can be given directly or as strike length × width across strike.
Sampling density is reported as samples per hectare (n ÷ (A ÷ 10,000)) so patterns can be compared across differently sized blocks. This is a geometric planning estimate only — it does not account for the orientation, continuity or true thickness of mineralisation, drill-hole spacing, resource-classification distances or QA/QC duplicates, all of which are set by the geology and the competent person.
Worked example
Grid spacing for 64 samples over a 200 m × 200 m block. A grade-control block is 200 m along strike by 200 m wide, giving an area of 40,000 m² (4 ha). You want to collect 64 samples on a regular square grid. Spacing = √(40,000 ÷ 64) = √625 = 25 m. So a 25 m × 25 m grid gives 64 sample points, a density of 16 samples per hectare.
Common mistakes
- Entering both a target sample count and a spacing — the tool needs exactly one of them, and derives the other.
- Confusing plan area with true area on a dipping structure: this is a plan (map-view) square-grid estimate, not a true-thickness or down-dip sample count.
- Treating the result as a resource-classification or QA/QC rule — grid spacing for measured/indicated resources is set by variography and geology, not by a simple √(area/n) grid.
Frequently asked questions
Does this give the spacing for a square grid or a triangular/staggered grid?
It assumes a regular square grid, where spacing = √(area ÷ number of samples). A staggered (triangular) grid gives slightly better coverage for the same count, so treat the square-grid spacing as a conservative first pass.
Can I use strike length and width instead of area?
Yes. Enter the strike length and the width across strike and the tool multiplies them (area = strike × width) before working out spacing or sample count. If you enter an area directly, that value is used instead.
Is this suitable for defining a resource or reserve?
No. This is a geometric planning estimate. Drill and sample spacing for Measured, Indicated and Inferred resources is governed by geological continuity, variography and the JORC/NI 43-101 competent/qualified person — always verify against site data and professional judgement.
What does samples per hectare tell me?
It normalises the pattern to a per-hectare density (1 ha = 10,000 m²) so you can compare sampling intensity between blocks of different sizes. A 25 m square grid is 16 samples per hectare.
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Tip: Enter any known values to calculate the remaining results.
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