FishRuler: Fish Size MeasureSupport
Have a question about FishRuler (fish size measuring and catch logbook), or found a bug? Do have a look through the FAQs below, then email us — we're happy to help. If measuring isn't working at all, the first thing to check is whether your iPhone has a LiDAR scanner.
FAQ
Which iPhones will it work on?
FishRuler measures using the LiDAR scanner, so it needs an iPhone fitted with one. That means the Pro models: iPhone 12 Pro / Pro Max and later. On a handset without LiDAR you'll see "This device does not support LiDAR" and measuring won't be possible. Please do check your model before purchasing.
Do I need to update iOS to use it?
Yes — FishRuler needs iOS 17 or later, as the logbook is built on Apple's newer on-device storage framework. If your iPhone can't update to iOS 17, the app won't install. Most LiDAR-capable iPhones run iOS 17 without any bother, but it's worth checking your software version before buying.
How do I use it?
Point the camera at the fish and tap once at the nose, once at the tail. A line is drawn between the two points and the distance is shown in centimetres. If a tap is out, drag the marker to fine-tune it, and press Reset to clear the measurement for the next fish.
Are my measurements saved? Can I look back at old catches?
Yes. When you save a measurement, it's added to your logbook along with a photo, species, location name and date, so you can browse past catches whenever you like. Nothing is saved automatically — you choose which measurements to log.
How does the personal best feature work?
Whenever you log a catch, FishRuler compares its length against the other entries you've logged for that species and marks it up if it's your longest yet. It's based only on what you've logged in your own logbook, not on any outside database.
Where does the release-size reference info come from?
It's drawn from a small set of publicly published regulations — national freshwater fishing byelaws and shared regional conservation sizes, for instance — for species and areas we could clearly document. It's shown purely as a reference alongside your measurement, not as an official ruling, and it isn't available for every species or area. Always check the current rules that apply where you're fishing.
How accurate is the figure?
The value on screen is a guide, based on what your device's depth sensor actually measures. Results are steadier in good light, with a steady hand, and with the fish laid as flat as you can manage. Treat it as a practical figure for use on the bank or the boat.
Can I use it for match measuring or size limits?
Please don't use it for that. For match measuring rules, minimum size limits set in law, or official record claims, always confirm with the measuring device those rules specify. Checking the regulations that apply where you fish remains your responsibility as the angler.
Does it work where there's no signal?
It does. FishRuler runs entirely offline. Rocky marks, upland streams, piers, out on the boat — it measures just the same with no reception at all.
Is there a charge? Is it a subscription?
It's a one-off purchase. Buy it once and there's nothing further to pay. No subscription, no in-app purchases and no adverts.
Are my photos or measurements sent anywhere?
No. Your logbook — photos, species, lengths, locations and notes — is stored only on your device. Nothing is sent to us or to any outside server, there's no account to sign in to, and the only time an image leaves your phone is if you deliberately choose to share a catch card.