You already know what your right hourly price is. However many clients are going to request a fixed price. Some may request this even before they have a specification.

You can give a fixed price if

• The specifications are well defined.
• You know how to handle change requests.
• You are good with estimating time
• You are comfortable with the client. (It requires experience and git feeling to decide which client will demand a lot of changes and insist they are part of the original specifications.)

If ALL of these do not exist, you should be very wary of committing to a fixed price quote and instead insist on a hourly/weekly pricing.

A year has 52 weeks, a week has 40 billable hours. So say a developer’s yearly salary is X$. Can you do X$/(52 * 40) to come to an hourly rate. Hell no.

You need to factor in

• Downtime when you are looking for clients
• Cost of infrastructure like servers, desktop and office space
• Vacations
• Insurance

A good rule of thumb is to take an yearly salary and divide that by 1000.

Of course many clients are going to ask for a fixed pricing. If you are comfortable with the client and specifications are well defined, you should provide a fixed quote.

Breakdown the specs in smaller unit of work. (Not larger than a day and then estimate the amount of work in hours. Multiply that by your hourly rate and add 20% margin as a contingency.) This should give you a guideline to do a fixed rate quote.