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Fish Weight Calculator

Estimate fish weight from length and girth measurements without a scale using species-specific formulas.

Reviewed October 7, 2026 Runs in your browser — inputs are never stored

Fish Weight Calculator

Weight (lbs)

2.16 lb

Weight (kg)

0.98 kg

This tool provides general sports and fitness estimates for educational purposes only. It is not medical advice — consult a physician before starting or intensifying training, especially if you have a cardiovascular condition.

About the Fish Weight Calculator

The fish weight calculator estimates a fish’s weight from length and girth, so you can record a catch without a scale and release it quickly. It uses standard angler formulas: length × girth² ÷ 1,200 for bass and most fish, ÷ 800 for trout and salmon, and length³ ÷ 3,500 for long, slim pike and muskie. Measurements are in inches.

How to use it

  1. 1Measure the length from the tip of the snout to the tail fork.
  2. 2Measure the girth around the thickest part of the body.
  3. 3Choose the species and read the estimated weight.

Worked example

an 18-inch bass with a 12-inch girth weighs about 18 × 144 ÷ 1,200 ≈ 2.2 lb (1.0 kg).

Common use cases

  • Catch-and-release records
  • Tournament estimates
  • Fishing logs

Frequently asked questions

A:For bass and most fish: weight (lb) = length × girth² ÷ 1,200 (inches). For trout and salmon the divisor is 800. Pike and muskie use length³ ÷ 3,500 because of their slim shape.

Reviewed for accuracy · Last updated October 7, 2026

Formulas follow published sports-science literature and official league definitions (Karvonen heart rate reserve, Cooper and Bruce protocols, MET compendium values, and standard baseball, cricket, and basketball statistics).

CW

CalcWisee Editorial Team

Calculator development and formula review

CalcWisee is an independent site founded by Ayman. Every calculator is built from a published formula or official definition, tested against hand-worked examples before it goes live, and corrected promptly when a reader reports an issue to ayman@calcwisee.com.

Expertise: Financial mathematics, Health and fitness formulas, Applied mathematics, Unit conversion standards

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