Work backwards from the money you keep
Start with the income you want before personal tax, add business expenses, then gross the total up by your combined tax rate: revenue equals income plus expenses, divided by one minus the tax rate. At a 30% rate, keeping $100,000 with $10,000 of expenses needs $157,142.86 of revenue before a single day is priced.
The gross-up is the step people skip. A rate built straight from the income target leaves the tax bill to be paid out of the money you intended to keep, which is why the order matters more than the arithmetic: expenses, then tax, then days.
The inputs are bounded so the division cannot break. Money fields run from $0 to $1 trillion, the tax rate is held between 0% and 80% - a 100% rate would divide by zero - billable days between 1 and 366, and billable hours a day between 1 and 24.
Billable days decide the daily price
Divide the revenue by the days you can actually bill. A full corporate year is roughly 220, but holidays, sickness and the admin and sales days nobody pays for all eat into it, and freelancers often land nearer 180. The default 220 is a starting point, not a promise about your calendar.
The effect is direct: the same $157,142.86 spread over 220 days is $714.29 a day, and over 180 days it is $873.02. Nothing about the work changed; only the number of days that produce an invoice did, which is why honesty about the days field moves the answer more than the rate you would like to charge.
The page also prints a weekly figure at five times the day rate, which assumes a five-day week regardless of the hours you enter. If your week is three billable days, treat the weekly line as a five-day benchmark rather than as your own capacity.
Turn the day rate into an hourly line
The hourly equivalent is the day rate divided by your billable hours a day, eight by default. At the defaults that is $89.29 an hour, the figure to sanity-check against salaried comparisons and against what the local market will pay for the same work.
It is also the number that catches an unrealistic day. Eight billable hours is a long day once admin, calls and revisions are added around it, so a day rate that looks reasonable can imply an hourly figure no client in your market will accept.
The display rounds the day count and the hours a day to whole numbers while the rates are computed from the exact values you typed. With a fractional day count - 220.5, say - the table shows 221 days but divides by 220.5, so the printed rows will not multiply back to the cent; the arithmetic is right, the display is simply shorter.
Where the day rate stops being a price
A day rate answers one question - what a day of your work has to earn to fund a year - and it answers it from the inputs on this page. It says nothing about the scope of that day: a client can buy eight hours and ask for twelve, and no arithmetic here will defend you against that.
Nor does it carry the rest of a small business: unpaid invoices, gaps between contracts, insurance, software, a laptop that dies mid-project. If any of those are material, they belong in the annual expenses field, because a day rate that funds only the income target quietly spends the business.
What the page will not do is set your floor for you. It prints the day rate, the revenue behind it and the hourly equivalent, so the figure can be checked against a market rate and against the salaried job it replaces; the judgment about what to ask for stays with you. An estimate, not a return, and not tax advice.
What a year of invoices actually pays
A rate is not a year. At $714.29 a day and 220 billable days the page shows $157,142.86 of revenue, but that assumes every one of those days is sold, invoiced and paid inside the year. Each unsold day is not a discount on the rate - it is 1/220th of the revenue gone, which is why a rate that looks comfortable can still leave a thin year behind it.
Payment terms move the same number again. On 30-day terms a full year of invoices sits in receivables for about a month on average: at $13,095 a month that is roughly $13,000 you have funded out of savings. On 60-day terms it doubles, and one client who pays at 90 days is financing 8% of your year for you.
The last line is bad debt. Writing off 2% of $157,143 loses $3,143 - the same as raising the rate by $14.29 a day and handing it back. A small reserve in the expenses field is the honest way to price that risk, rather than hoping no invoice ever goes unpaid.
Danfio