A yearly salary from an hourly wage is the rate × the hours a week × the paid weeks a year. At the usual 40 hours and 52 weeks that is 2,080 paid hours, so $25 an hour is $52,000 a year, and a salary divided by 2,080 gives its hourly rate: $60,000 is $28.85 an hour.
Paid weeks. 52 weeks assumes holidays are paid, as they are for most salaried jobs. If time off is unpaid, for a contractor or an hourly job without paid leave, lower the weeks: two unpaid weeks turns $25 an hour into $50,000 a year, not $52,000. Part-time work changes the hours, so 20 hours a week at $25 is $26,000.
Pay periods. Weekly and every-two-weeks pay follow the weeks worked. Twice-a-month and monthly pay are simply a 24th and a 12th of the year, so a month is not four weeks: $52,000 a year is $4,333.33 a month but $4,000 for four weeks. That gap is why a monthly budget built on "four paychecks" runs short.
Before tax. These are gross figures, before income tax, social security and pension contributions, and the currency picker only relabels the amounts. For take-home pay under India's tax regimes, use the CTC calculator.