Fish Weight Estimator
Fill in the values and the answer updates as you type.
How the Fish Weight Estimator works
Uses the common angler's formula: weight in pounds = length × girth² ÷ 800, with both measurements in inches. Centimeters are converted to inches first. It is an estimate that is usually within about 10% for typical freshwater fish. Very slim, very deep, or pre-spawn fish can differ, and a certified scale is always the real weight.
Inputs and results
The Fish Weight Estimator takes 3 inputs and gives 3 results.
What you enter
- Fish length (nose to tail fork) — starts at 24.
- Girth (around the thickest part) — starts at 15.
- Measurement unit — starts at Inches. Choose from: Inches and Centimeters.
What you get
- Estimated weight (lb)
- Estimated weight (kg)
- Estimated weight (oz)
Example: Fish Weight Estimator with the starting values
With fish length (nose to tail fork) 24, girth (around the thickest part) 15 and measurement unit Inches, the calculator returns:
| Estimated weight (lb) | 6.75 |
|---|---|
| Estimated weight (kg) | 3.06 |
| Estimated weight (oz) | 108 |
Change any value above and the results update straight away.
Fish Weight Estimator FAQ
How do I use the Fish Weight Estimator?
Enter fish length (nose to tail fork), girth (around the thickest part) and measurement unit in the fields, then read estimated weight (lb), estimated weight (kg) and estimated weight (oz) in the result panel. The answer updates as you type, and you can press Calculate or Enter to refresh it. Use “Copy link” to share your exact numbers with someone else.
What does the Fish Weight Estimator calculate?
Estimate a fish's weight from its length and girth before you release it. It returns estimated weight (lb), estimated weight (kg) and estimated weight (oz) from the 3 values you provide.
What values does the Fish Weight Estimator start with?
It opens with fish length (nose to tail fork) 24, girth (around the thickest part) 15 and measurement unit Inches so you can see a working result straight away. Replace them with your own numbers, or press Reset to return to these starting values.
Is the Fish Weight Estimator free and private?
Yes. It is free, needs no account, and runs in your browser, so nothing you type is sent to or stored on our servers. See the Privacy Policy for details.
Can I rely on the Fish Weight Estimator for important decisions?
Treat the result as a well-rounded estimate. Real situations often have details a general calculator cannot know, so confirm important decisions with a qualified professional. See the Disclaimer for more.