How it works
The common rule of thumb is about 5 feet of depth per lead-core colour at roughly 2 mph. This calculator scales that by 2 ÷ speed, so slower trolling runs deeper and faster trolling runs shallower. Thinner lead core also sinks more per colour.
Frequently asked questions
How exact is this?
Not exact. Lure weight, line diameter, turns and current all move the real depth. Use it to get in the zone, then confirm with a fish finder or by touching bottom.
What if I troll much slower or faster?
The adjustment is a rough guide only. Very slow or very fast trolling changes lure action as well as depth.
Does this work for other line types?
No — this rule is for lead core. Snap weights, downriggers and diving lures follow different rules.