Lure Trolling Depth Calculator
Estimate how deep a lure runs when trolling based on line diameter, trolling speed, and amount of line out.
Plan your trolling presentation.
When trolling, the depth a lure runs depends on the line diameter (which creates water resistance and drag), the amount of line out, and the trolling speed. Faster speeds push lures shallower; thinner line allows them to run deeper.
Simplified depth formula: Depth ≈ (Line out in feet × lure drag factor) / (speed factor × line diameter factor)
This is an approximation — actual depth varies significantly by lure type, weight, and lip angle. Manufacturers publish depth charts for specific lures (e.g., Rapala, Bomber). Divers and weight systems (snap weights, downriggers) reliably control depth.
General rule of thumb for crankbaits:
- Every 10 ft of monofilament out: dives ~1 ft (slow, thin line)
- With 0.008" diameter mono at 2 mph: roughly 1 ft per 10 ft of line
- With 0.011" mono: roughly 1 ft per 12 ft of line
- Increasing speed from 2 to 3 mph reduces depth by ~30%
Depth control options:
- Lead core line: color-coded, each color is 10 yards, dives about 5 ft per color
- Snap weights (in-line weights): add 1–3 oz to run 5–15 ft deeper
- Downriggers: precise depth control, lure releases at strike
- Diving planes (Dipsy Divers): run 30–60 ft deep
The best approach: use a depth finder to confirm fish location, then adjust presentation until you match that depth.