A related question came up recently:

I'd like to power my new LG M2450D monitor with a basicXL BXL-NBT-U02 universal AC-DC power adapter. This PSU is rated 90W max and supports 15-24V output voltage. The original monitor PSU (PA-1650-68) was fixed at 19V and 3.32A.

Now, doing the math: 90W / 19V = 4.74A

Of course this is an ideal value, what is "safety margin" i should assume for the real max amperage?

To be conservative in the face of ambiguous specifications like these, you should assume that the maximum power rating of the universal adapter occurs at the maximum output voltage, and that all lower output voltages are limited to the same current.

In this case, 90W/24V = 3.75A, so you should be good to go with the output set at 19V with this amount of current.

A related question came up recently:

I'd like to power my new LG M2450D monitor with a basicXL BXL-NBT-U02 universal AC-DC power adapter. This PSU is rated 90W max and supports 15-24V output voltage. The original monitor PSU (PA-1650-68) was fixed at 19V and 3.32A.

Now, doing the math: 90W / 19V = 4.74A

Of course this is an ideal value, what is "safety margin" i should assume for the real max amperage?

To be conservative in the face of ambiguous specifications like these, you should assume that the maximum power rating of the universal adapter occurs at the maximum output voltage, and that all lower output voltages are limited to the same current.

In this case, 90W/24V = 3.75A, so you should be good to go with the output set at 19V with this amount of current.