Can you test the actual amperage of a 120v home outlet with a multimeter?
When I plug in an appliance over 10amps in the 15amp outlet, the GFI kicks off. I want to test the outlet to see exactly how many amps are available. Thanks

You are wasting your time trying to test the amperage on a vacant receptacle.

To determine the available amperage, check the breaker for that circuit. That's what limits the amperage.

The GFCI does not trip because of an inrush of amperage. It monitors the difference between in amperage between the constant Hot (Black) conductor and the Neutral (White) conductor. In a correct environment, if there are 5 amps on Black, there should be 5 amps on White. If the GFCI senses 5 amps on Black and 5.6 amps on White, the GFCI will open killing the power from the outlet.

To be honest with you, you really need to know what amperage is being drawn over the total circuit and then add the 10+ amps and see if you are creating an overload condition.

Don is right on. The amps of the whole circuit are available at every receptacle or outlet on the circuit.

Here is my reply in the other thread you started: https://www.askmehelpdesk.com/electrical-lighting/testing-breaker-amperage-multimeter-309024.html