Category: Guides

Lead core line is one of the simplest ways to get a lure down to fish without downriggers or heavy weights — and the colors aren’t just for looks. Each color tells you how much line is out, which tells you roughly how deep your lure is running. Here’s how to read it.

What lead core line is

Lead core is a braided or woven line with a soft lead wire running through the center. That weight makes it sink as you let it out behind a moving boat. The line is dyed in repeating 10-yard segments, each a different color, so you can count how many segments — “colors” — you’ve deployed.

The “rule of fives”

The classic rule of thumb for standard 18 lb lead core is about 5 feet of depth per color at a trolling speed near 2 mph. Each color is 30 feet (10 yards) of line, so a full core of ten colors is 300 feet of lead. Let out five colors and you’re running roughly 25 feet down; let out eight and you’re near 40 feet.

Speed changes everything

Depth per color is not fixed — trolling speed has a huge effect. Slow down and the line sinks deeper, up to five or six feet per color. Speed up and the line planes higher in the water, averaging closer to two or three feet per color. Even a tenth of a mile per hour makes a measurable difference, which is why consistent boat speed matters when you’re trying to repeat a depth that’s producing fish.

Counting colors as you go

Let line out steadily and count each color change as it leaves the reel. Many anglers note the depth a fish hit by remembering how many colors were out, then return to that exact count. Adding a monofilament or fluorocarbon leader between the lead core and the lure keeps the heavy line away from the bait and gives a more natural presentation — just remember the leader adds a little extra depth and distance.

Standard vs thin lead core

Newer thin-diameter lead cores cut through the water with less resistance and sink faster — often around seven feet per color instead of five. If you switch line types, your old color-to-depth math changes, so recalibrate rather than assuming the same numbers.

Estimate your depth instantly

Skip the mental math on the water. Our free trolling depth calculator turns colors out, speed, and line type into an estimated running depth in seconds — a great starting point before you fine-tune with a depth finder.

Related from Fishing Toolbox

• Braid vs Mono: How Much Line Really Fits on Your Reel
• How to Set Your Fishing Drag the Right Way

Drag is the quiet hero of every fight. Set it well and a big fish tires itself out against smooth, steady pressure. Set it wrong and you either snap the line on the hookset or watch a trophy throw the hook because there was never enough tension. Here’s how to dial it in every time.

What drag actually does

Your reel’s drag is a friction system that lets line slip out under load before it reaches its breaking point. When a fish surges, the drag gives line instead of letting the rod and line take the full force. The goal is to apply the most pressure you can without risking a break — enough to control the fish, not so much that a sudden run pops the line.

The 25–33% rule

A reliable starting point is to set your drag to one-quarter to one-third of your line’s rated breaking strength. So for 20 lb line, that’s roughly 5 to 6.6 lb of drag pressure. Starting at the lower end gives you a safety margin; you can always add pressure during the fight, but you can’t take back a break.

How to set it with a scale

Guessing by pulling line off the spool with your hand is better than nothing, but a simple spring scale makes it exact. Tie your line to the scale, hold the rod at the angle you’d fight a fish (tip up, loaded), and pull until line just begins to slip. Adjust the drag knob or star until the scale reads about a quarter to a third of your line test. Do this with the same knot and line you’ll actually fish.

When to back off

• Light leaders: if your leader is weaker than your main line, set drag to the leader’s strength, not the main line’s.
• Fish near structure: heavy cover can mean you need to lighten up so a head-shake doesn’t snap you off — or tighten down to turn fish, depending on your strategy.
• Treble hooks and soft mouths: species like crappie or trout tear out easily; a lighter drag protects the hook hold.
• Near the boat: a fish’s final lunge boatside breaks more line than the whole fight. Be ready to thumb the spool or ease the drag.

Common mistakes

The two biggest errors are fishing with the drag cranked all the way down “so the fish can’t take line,” and never checking it after it’s been sitting. Drag washers settle and stiffen over time, and a reel left fully tightened can develop a sticky, jerky drag. Back the drag off when you store a reel, and re-check the setting at the start of every trip.

Let the calculator do the math

Not sure what a quarter to a third of your line works out to? Our free drag setting calculator gives you the recommended drag range the moment you enter your line’s pound-test — so you know exactly what to aim for on the scale.

Related from Fishing Toolbox

• Braid vs Mono: How Much Line Really Fits on Your Reel
• How to Estimate a Fish’s Weight Without a Scale

Whether you’re chasing a personal best, fishing a catch-and-release tournament, or just settling a friendly bet at the boat ramp, knowing what your fish weighs matters. But carrying a scale isn’t always practical, and hanging a fish on one long enough to get a reading is hard on a fish you plan to release. The good news: you can get a reliable weight estimate with nothing but a tape measure and a little math.

The formula that actually works

For most fish, weight is closely tied to two measurements: length and girth. The formula anglers have trusted for decades is:

Weight (lb) = (Length × Girth × Girth) ÷ 800 — with length and girth both measured in inches.

Girth is the key. Two fish of the same length can weigh very differently — a fat, well-fed bass carries far more than a long, skinny one. Because girth captures how heavy-bodied a fish is, this method is usually accurate to within 5–10% of the true weight for a fish in average condition.

How to measure your fish

Length: Lay the fish flat and measure from the tip of the nose to the end of the tail. Keep the tape straight along the body.

Girth: This is the distance all the way around the fish at its fattest point — usually just behind the gills and pectoral fins. Wrap a flexible tape (or a piece of fishing line you measure afterward) snugly around the body. Don’t cinch it tight; just bring it flush against the fish.

Match the formula to your species

The 800 divisor works well for thicker-bodied fish. Leaner, more streamlined species carry less weight for their length, so they use a slightly larger divisor of about 900:

• Divide by 800: largemouth and smallmouth bass, catfish, panfish
• Divide by 900: trout, walleye, northern pike, muskie

Using the right divisor keeps slim fish from being overestimated and heavy-bodied fish from being shortchanged.

A worked example

Say you land a largemouth bass that’s 18 inches long with a 12-inch girth. Plug it in: (18 × 12 × 12) ÷ 800 = 2,592 ÷ 800 = 3.24 lb. A quick, repeatable number — no scale required.

No way to measure girth? Estimate from length

If all you have is a length, you can still ballpark the weight, but expect it to be rougher — a length-only estimate has to assume an average body shape, and real fish are fatter or thinner than average. Treat it as a guide and add girth whenever you can for a number you can actually trust.

Tips for a more accurate estimate

• Measure quickly and keep the fish wet and calm, especially if you’re releasing it.
• Measure girth at the widest point, not back toward the tail.
• Pre-spawn females run heavy — a fish full of eggs can weigh 10–20% more than the formula suggests.
• For an official record, an estimate never counts; only a certified scale does. The formula is for everyday use and release fishing.

Skip the math — use the free calculator

Don’t want to do arithmetic with cold, wet hands? Our free fish weight calculator does it for you: choose your species, enter length and girth, and it instantly returns the weight in pounds, ounces, and kilograms — using the exact formula above, with the right divisor already built in for each species.

Related from Fishing Toolbox

• Smallmouth Bass Length to Weight Chart
• Largemouth Bass Length to Weight Chart