Start with your desired annual take-home — the number you want to actually keep in your bank account after taxes and business costs. Don't anchor on an old salary; anchor on the lifestyle you want to fund.
Set billable hours per week realistically. This is the time you can actually invoice for, not your total working hours. Solo freelancers typically lose 30–50% of their week to sales calls, proposals, admin, accounting, marketing, and learning — none of which clients pay for directly. Starting at 20–25 billable hours and adjusting as you measure your real ratio is sensible.
Pick vacation weeks honestly. You're the boss, so unpaid time off is real money out of pocket. Four weeks (US standard PTO equivalent) is a good baseline; add more if you take a long winter break or sick weeks.
Enter your annual business expenses — software subscriptions, hardware refreshes, accounting fees, coworking, professional development, and any pass-through costs. Then set the combined tax rate: federal income tax + state income tax + self-employment tax (~15.3%). For most US freelancers, 25–35% is realistic.