Estimated depth
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ft
How deep your sinker or lure is actually running, from the line you have out, your speed, your sinker weight and your line diameter. An estimate — verify it against your depth finder.
| Speed | Depth (ft) | Depth (m) | Line angle |
|---|
Your line hangs in the water at an angle set by two competing forces: the weight pulling it down and the drag of the water pushing it back. Drag increases with the square of your speed and with line diameter, which is why speeding up lifts your lure so sharply.
The calculator balances the effective weight of the sinker in water against the drag on the line, and reports the resulting depth. It assumes calm water, a sinker fished off the bottom, and a relatively straight line — all reasonable approximations for a first pass, but approximations nonetheless.
Three levers, in order of effectiveness:
1. Slow down. Halving your speed cuts drag roughly fourfold. This is the most underused way to gain depth.
2. Go thinner. Braid of the same pound test is far thinner than mono, so it creates less drag and runs deeper on the same weight.
3. Add weight. Effective but blunt — too heavy and you lose feel, and you risk hanging up on bottom.
A dedicated diving device such as a downrigger, dipsy diver or lead-core line beats all three for precision, at the cost of setup time.
A sinker selection, thin line, and a way to measure how much line you actually have out.
Thin diameter means less drag and more depth. Also no stretch, so bites register at the rod tip.
Check current price on Amazon →Weight is how you coarse-tune depth. Buy the range — current and depth both move what you need.
Check current price on Amazon →"About 80 feet" is the main source of error in trolling. A line counter makes it repeatable.
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Full detail for every calculator is on the methodology page.
Line out is only one of three things that set trolling depth. The downrigger depth calculator handles the cable-and-ball side, the crankbait diving depth chart covers baits that dive on their own, and the water temperature chart tells you which depth is worth targeting. Much of that trolling targets salmon, trout and walleye, and the fillet yield calculator shows what those fish give up on the cleaning table.
It is an estimate based on line diameter, sinker weight, trolling speed and the amount of line out. Actual depth varies with current, line age and whether your sinker is touching bottom. Treat the number as a starting point and adjust against what your depth finder reads.
Because drag on the line increases with the square of speed. Double your speed and the drag roughly quadruples, which lifts the line and pulls your lure up. Slowing down is the fastest way to get deeper without adding weight.
Braid, because it is much thinner than monofilament of the same pound test. Less diameter means less drag, which means more depth for the same weight and speed. Braid has no stretch either, so bite detection is far better at depth.
It depends on speed, weight and line diameter, but with 20 lb monofilament at 1.5 mph and a 1 oz sinker you need roughly 100 feet of line out to reach about 25 ft; at 2 mph the same 100 ft only reaches about 20 ft. Braid of the same rating needs considerably less. Run your own numbers through the calculator above.
Both matter, but they trade off against each other. Adding weight gets you deeper at the same line length, and letting out more line gets you deeper at the same weight. Weight gets you down faster; line length is how you fine-tune once you are close.
Line Diameter Converter · Sinker Weight Converter · Fishing line strength chart · Crankbait depth chart · Fishing seasons chart
Weight and depth: Lure Weight Calculator · Jig Head Weight Calculator · Sinker Weight Converter · Lure Sink Rate Calculator · Downrigger Depth Calculator
Line and leader: Braid to Mono Converter · Line Diameter Converter · Reel Line Capacity Calculator · Shock Leader Calculator · Fly Leader Length Calculator
Knots and hooks: Knot Strength Calculator · Hook Size Selector
Reel, drag and cast: Reel Gear Ratio Calculator · Casting Distance Calculator · Drag and Leader Calculator
Fish and catch: Fish Weight Calculator · Fillet Yield Calculator · Fly Line Weight Calculator
Reference charts: Crankbait Diving Depth Chart
Estimates only: the values shown are a starting point, not a guarantee. Products of the same stated size differ between makers, so your own result will vary. TackleCalc is not affiliated with any manufacturer, and these figures are a guide rather than a guarantee.