What actually lands in your account, and what your pay is worth once inflation is accounted for. Two different questions, and most tools answer neither one carefully.
The Australian pay calculator asks the question the rest of the category does not: is the figure you are entering before tax or after it? Most people know their take-home, because it is the number in their account - and entering it into a gross field gets you a confident answer to a question you did not ask. This one solves the tax scale backwards instead. It also uses 26.089 fortnights a year rather than 26, which is the difference between agreeing with your payslip and being a few hundred dollars out.
The real wage calculator converts a salary between years using actual inflation data, so you can see whether a raise kept pace. It works in both directions: what an old salary is worth in today money, and what you would need to earn now to match a past standard of living. It also solves the question people usually want answered but rarely phrase directly: what figure do you need to ask for, to genuinely be ahead rather than standing still?