Gram-metre calculator

How it works

Gram-metres put a long, modest intercept and a short, rich one on the same scale: 50m at 2g/t (100 g-m) carries as much gold per metre of strike as 10m at 10g/t (100 g-m). Stockhead's rule of thumb for gold is that over 50 is good, 100-200 really good, 200-500 excellent, and anything beyond that stellar. For copper DrillScore uses %-metres with its own bands - see the methodology.

The two adjustments that matter

• True width. If the hole cuts the mineralisation at an angle, the down-hole interval is longer than the zone is thick. Enter the true-width percentage the company gives (or estimate it) to see the gram-metres the zone actually holds. True width explained.
• Smearing. Enter the richest "including" sub-interval to see how much of the total it supplies. If one metre carries most of the gram-metres, the rest of the interval is much lower grade than the headline suggests. Smearing explained.

Every intercept DrillScore decodes is ranked on the drill results leaderboard.