The level indication at instruments with an output or input of 50 Ω takes place usually in decibels relative to 1 mW (dBm).
The indication in watts (W), milliwatts (mW) or microwatts (µW) is often important for amateur radio operators.
Both values can be converted into each other with the following scripts.

The first script calculates the power at 50 Ω in watts (W), milliwatts (mW) or microwatts (µW) in decibel relate to 1 mW (dBm).

The second script calculates from the power in decibels relative to 1 mW (dBm) the power at 50 Ω in watts (W), milliwatts (mW) or microwatts (µW).

If you want to know, how looks the equation used into the scripts, then see at the mathematical background: conversion.