How to measure i/o latency separately?

[bencuri]

There are directions on Youtube on how to measure audio roundtrip latency with looping the audio out and input on your interface and making a test recording this way. However, some DAWs, like Reaper, is asking for adding input and output latency values separately, not the roundtrip latency, that is the summary of the two. How can you measure these separately? Or is there a formula to calculate each from roundtrip latency?