NUMA — the lenses you own and the one you want, on the same focal-length scale

Type in the cameras and lenses you own, and they line up along a focal-length scale. Everything stays on this device. No account, no sign-in.

What it does

Type a lens by name and it lands on a focal-length scale. Primes are ticks, zooms are bars.
What you own is solid, what you want is dashed, on the same scale. Before you buy, you can see whether that lens overlaps what you already have.
The scale is logarithmic. Even spacing would crush the wide end, and the more wide lenses you own, the less you could read.
One view shows where your focal lengths bunch up and where the gaps are. The app does not point at the gap; you do.
Pick the gear you want and get one card image to share.

People about to buy another lens who want to check it against what they own.
People whose lens list has grown past what they can recite.
People who would rather see overlap and gaps as a shape than keep them in their head.

Open numagear.com in a browser and start.
On iPhone and Android, add it to the home screen and it opens like an app (PWA).
If you do not sign in, your gear never leaves the device. Signing in is optional.

Free for up to three items (camera bodies and lenses together).
From the fourth, a licence key removes the limit: 20 US dollars, paid once. No subscription.

There are still gaps. Values we do not know are left blank rather than guessed.