For services (e.g. consultancy/ hair & beauty / plumber, childcare and of course a web design freelancer etc), the time based costing formula is as follows:
ANNUAL OVERHEADS
ANNUAL AVAILABLE PRODUCTIVE HOURS = Rate per hr (breakeven)
(Hours x Days x Weeks)
The average person living in the UK would realistically need a minimum survival budget of £20k after tax to live on. A freelancer would have nominal operational overhead; a vehicle, small materials expense, phone, office expenses, insurances, webhosting, marketing, etc, but still less than £10kpa on average. Now the average productive hours (that means time spent on a client's job or with the client, but excluding one's own time on book-keeping, etc is approx six hours a day) multiplied by working a five-day week, 48 weeks of the year, allowing for illness and holidays, give us:
E.g:
£30000 = £21.00 Per Hour (rounded up Breakeven)
6 x 5 x 48
(1,440 hours)
The above example is based on one person as a 'fee-earner' and only covers costs. To improve lifestyle and reinvest in the venture, a target profit would realistically need to be reflected in a price to the customer of at least £50 per hour. This is because of an axiom called "The thirds rule": a third of your profit will go in tax; a third is for you, the other third is to re-invest in the business to grow it (to add staff, contribute to replacing equipment, a vehicle, etc). This helps set a sales target....
Therefore there is a benefit of having other 'fee-earners' working for you (we need back office staff to handle admin and other functions, but a fee-earner is someone who is directly influencing sales by duplicating your own efforts). This is because you can multiply the number of productive hours. Even though your overheads would be higher, the bottom figure in the equation would reflect a lower hourly rate overall, thus:
E.g:
Venture with 3 fee-earner staff, each paid £15,000pa, plus yourself (if you decided to keep working 'in' your business, more than 'on' it!):
£75000 = £13.02 Per Hour (Breakeven)
4 x 6 x 5 x 48
(5,760 hours)
Point being, it's more cost-effective in the longer run to employ fee-earning people (or outsource) than trying to do it all oneself.
There's a different calculation for product sales....
I've been a qualified freelance Business Start-Up advisor for over 15 years and run my own training company.....hope that helps!