What hourly to salary conversion is doing
At its simplest, converting hourly pay to salary means multiplying the hourly rate by the number of paid hours worked in a week and then by the number of paid weeks in a year. That gives a gross annual earnings estimate before tax or deductions. A free online calculator makes that comparison much faster when you are moving between hourly and salaried pay figures or comparing jobs with different schedules.
This kind of calculation tool is most useful when the schedule is stable. If your hours change every week, the result is still a planning estimate rather than a guaranteed yearly total. That matters especially for shift work, seasonal work, unpaid time off, and roles where overtime is occasional rather than part of a regular pattern.