Every fish finder gets a score from 0 to 100% built from five factors, which maps onto the 5-point rating shown on the site (a 0% score would be 1.5 stars; a perfect score, 5). Each factor is scored against fixed reference points, not against the other products in the list, so adding a new model never moves another model’s rating. Fish finders are grouped by screen size, up to 7 in and over 7 in, and value has its own scale for each group.
| Factor | Measures | Weight |
|---|---|---|
| Value | price per inch of screen | 30% |
| Sonar | CHIRP, down imaging and side imaging with the transducer in the box | 25% |
| GPS and maps | built-in GPS and preloaded maps | 15% |
| Screen | pixels per inch | 10% |
| Warranty | warranty length | 20% |
Where the numbers come from
Screen size, resolution, sonar types, GPS, maps and warranty come from the maker’s spec page or manual, for the display and the transducer bundled with it under one part number. Prices are checked at Amazon, the maker’s own store and fishing retailers, and the lowest is used.
The factors
Value is the current price divided by the screen diagonal, on a log scale, so halving the price per inch always counts the same. For screens up to 7 in, $150 per inch scores zero and $30 full marks; over 7 in, $300 and $60.
Imaging scores the sonar views the transducer in the box gives: CHIRP sonar counts 30%, down imaging 35% and side imaging 35%. A unit that can add side imaging only with a separate transducer gets no credit for it.
Mapping is zero with no GPS, 40% with GPS but no maps, 70% when maps go on a card and full marks when lake or coastal maps come preloaded.
Screen is sharpness in pixels per inch: 100 scores zero and 220 full marks.
Warranty is the maker’s warranty: 1 year scores zero and 3 years full marks.
What isn’t scored
Touchscreen, forward-facing live sonar support, maximum depth, wifi pairing and networking are listed but not scored. The transducer in the box is named on each product page.
Missing data
If a figure isn’t published, that factor gets the neutral middle score (50) and the product page marks it as estimated.
Ties and discontinued models
Products are ranked by score within each group. Discontinued models stay listed but rank below every current model and can be hidden with the “Hide discontinued” filter.