Gape Width by Bait Diameter Calculator

So you’ve got all of those fancy lures in the tackle box. You take ’em out on the water and something doesn’t work right. They get ’em to chase them down. They slap them around. But then they get away before hook ever sets. It becomes a frustrating puzzle.

Then one day you put two and two together and come up with four; that’s not usually the color or the action; it’s almost always the fit. An eighteen-inch largemouth bass doesn’t have an eighteen-inch-wide mouth. And knowing difference between bait diameter and gape width will change everything on every cast. Because it’ll shift emphasis off of what looks good to what realy fits.

Why Bait Fit Matters More Than Size

After choosing your target species and entering your lure size, the calculator (above) do the rest for you. All you do is enter largest diameter your bait will fit into (not the total length), since this is where the bait gets stopped up. From there, it calculates approximate inner width of the fish’s mouth from biological models and how it relates to the shape of your lure.

In other words, it gives you an idea if you’re offering them something they can handle or something so big they hesitate and don’t bite. In short, it makes a complicated shape question easy, can I expect him to eat it? Or not?

Most anglers judge their baits by length. That’s also what gets written on the package, so a six inch swimbait sounds big right? It sounds big until you realize it is wide enough to wiggle through narrow, moving opening. Width are the limiting factor there.

Hard baits don’t give, but soft plastics will compress a bit under pressure. This makes a huge difference when trying to match the hatch or trick picky trout. The tool consider this with questions regarding expected compression and profile of the bait. A flat sided worm of the same nominal size as a round grub will slip into a tighter space easier, for instance. Ignoring that means you’ll overestimate what fits, causing you to miss opportunities and fish you could of caught.

Finally, there’s the hook gap. This one is something you don’t really think about until you’re out there and can’t seem to get it through the fish’s lip. The bait fits into the mouth, but point of the hook isn’t exposed enough to go through once they bite. To make sure we have enough gap for penetration on the trigger bite, the calculator measure hook exposure. An offset hook needs more room than say a bare jig does, depending off how much bulk and weight is hanging off of it in the fish’s mouth. That is also why they use smaller hook gaps and lighter offerings like a Texas rigged worm. This maximize their chance to find the hook instead of simply riding down the top of the fish’s mouth.

Bait size is an important factor to a bass’s preference but even more so with fish that have become very particular. They can get picky depending on water conditions. When the water is more clear, it has to be exact. They want to look at their meal and if something doesn’t pass the test they won’t touch it. That’s why the calculator also takes into account margin of strike conditions. So if something would work in the summertime when they’re aggressive and metabolisms is high, it may be ignored when the weather cools down and a front blows through. Lastly, it allows you to avoid the head scratching of throwing a big bait when a little one should do the trick.

To conclude, Matching your presentation with the physical limitations of your quarry are always a big key to catching more fish. But larger does not necessarily mean bigger. In fact, sometimes downsizing drastically gets your bait past what it will accept. The gape width concept remind us there are some hard boundaries in nature. Even though you may be using the best retrieve in the world, it won’t matter if the geometry is off. Respect the mouth size limits and keep the proportions sensible and you’ll be sure to have fewer misses and happier days of fishing and trips home. This simple principle can make a good angler into a great one because it focuses on what realy gets swallowed as opposed to what merely looks impressiv from the boat deck.