FishRuler: Fish Size MeasureSupport
Got a question about FishRuler (fish size measuring and catch logbook), or found a bug? Have a look through the FAQs below, then shoot us an email — happy to help. If it won't measure at all, first thing to check is whether your iPhone has a LiDAR scanner.
FAQ
Which iPhones does it work on?
FishRuler measures with the LiDAR scanner, so you need an iPhone that's got one. That's the Pro models: iPhone 12 Pro / Pro Max and newer. On a phone without LiDAR you'll get "This device does not support LiDAR" and measuring won't work. Worth checking your model before you buy.
Do I need to update iOS to use it?
Yeah — FishRuler needs iOS 17 or later, since the logbook runs on Apple's newer on-device storage framework. If your iPhone can't get to iOS 17, the app won't install. Most LiDAR iPhones handle iOS 17 fine, but worth checking your software version before you buy.
How do I use it?
Point the camera at the fish and tap once on the nose, once on the tail. A line is drawn between the two points and the distance comes up in centimetres. If a tap's off, drag the marker to fine-tune it, and hit Reset to clear it for the next fish.
Are my measurements saved? Can I look back at old catches?
Yeah. When you save a measurement it goes into your logbook with a photo, species, location name and date, so you can flick back through past catches whenever. Nothing gets saved automatically — you choose what goes in the logbook.
How does the personal best thing work?
Every time you log a catch, FishRuler checks its length against the other ones you've logged for that species and flags it if it's your biggest yet. It's only working off what's in your own logbook, not some outside database.
Where does the release-size reference info come from?
It comes from a small set of publicly published rules — national freshwater fishing regs and shared regional conservation sizes, for instance — for species and areas we could clearly source. It's shown purely as a reference next to your measurement, not an official ruling, and it's not there for every species or area. Always check the current regs where you're fishing.
How accurate is the number?
The figure on screen is a guide, based on what your phone's depth sensor actually reads. You'll get steadier results in good light, with a steady hand, and with the fish laid as flat as you can get it. Treat it as a practical number for out on the water.
Can I use it for comp measuring or legal size limits?
Please don't. For tournament measuring rules, legal size limits, or official record claims, always confirm with the measuring device those rules call for. Checking the regs where you fish is on you as the angler.
Does it work where there's no reception?
Yep. FishRuler runs completely offline. Off the rocks, up a freshwater creek, on the breakwall or out wide on the boat — it measures the same with no bars at all.
What does it cost? Is it a subscription?
It's a one-off purchase. Buy it once and there's nothing more to pay. No subscription, no in-app purchases, no ads.
Do my photos or measurements get sent anywhere?
No. Your logbook — photos, species, lengths, locations and notes — stays on your device only. Nothing gets sent to us or any outside server, there's no account to sign into, and the only time a photo leaves your phone is if you deliberately choose to share a catch card.