The two halves
Five gallons in the can at 50:1 needs 12.8 ounces of oil. US, metric or imperial, and the gas and oil units are chosen separately.
The other direction, which is the one you actually need in the shed: there is a partial bottle of oil on the shelf, so how much gas does it mix with?
Trimmer, blower, chainsaw, outboard, snow blower. Each keeps its own ratio, and tapping it sets the calculator for that machine.
Spark plug, air filter, fuel filter, blade. The reason to open this app standing in a hardware-store aisle.
What you did and when, per machine. So next spring you know whether that carburetor was already rebuilt.
No signal in the garage is fine. It loads once and then it is just there.
Your data
There is no account, no sign-in and no server. Every machine, photo and service record is stored on your device and nowhere else — which also means a lost phone is a lost list, so the app can export a backup file you keep yourself.