Fishing Sinker Weight Calculator
Estimate how heavy a sinker you need to hold bottom in current, based on water depth and current speed.
How it works
weight (oz) ≈ (0.6 × current² + 0.03 × depth) × rig factor, rounded to the nearest ½ oz
The force trying to sweep your rig off the bottom rises roughly with the square of current speed, so doubling the current calls for far more than double the lead. Deeper water means more line in the flow and more drag, which this estimate adds in linearly, and surf rigs need extra to punch through breaking waves and swell. Start with the suggestion, then add weight until the sinker stops tumbling — the goal is the lightest lead that stays put.
Worked example
In a 2-knot current at 20 ft on a bottom rig: (0.6 × 2² + 0.03 × 20) × 1 = (2.4 + 0.6) = 3.0 oz. Switch to surf casting (×1.25) and it rises to about 3.5–4 oz.
Frequently asked questions
What size sinker do I need for strong current?
It scales with the square of speed, so strong flow may need 4–8 oz or more. Add weight until the sinker holds instead of dragging, and consider a grip/pyramid style that digs in.
Does sinker shape matter?
Yes. Pyramid and grip-lead shapes bite into sand and hold in current far better than round sinkers of the same weight, so shape can matter as much as ounces.
Why start light?
The lightest lead that holds gives the most natural presentation and better bite detection. Over-weighting kills sensitivity and can spook fish, so add only as much as the current demands.
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This calculator is for educational purposes. Double-check important results before acting on them.