Hourly pricing is the default. It's not always the best option — especially as you get more experienced and efficient.
Hourly pricing penalizes you for getting faster and better at your work. A task that takes a junior 10 hours and a senior 2 hours earns the senior less under hourly billing — even though the senior delivers more value. As you gain experience, project-based or value-based pricing often serves you better.
A fixed price for a defined deliverable. Works well when scope is clear, you have experience estimating the work, and the client values certainty. Include a clear scope in the contract — scope creep is the main risk.
Even if you move to project pricing, knowing your minimum hourly rate (from the calculator) tells you when a project is profitable and when it isn't. Divide the project fee by your estimated hours — if the implied hourly rate is below your minimum, the project loses money regardless of how it's framed.