Free Invoice Calculators
Small, fast tools for the numbers around an invoice — due dates, late fees, early-payment discounts. Everything runs in your browser: nothing you type is sent or stored. Every calculator pairs with the free invoice generator.
Payment terms & deadlines
Due Date Calculator
Invoice date plus Net 7–90 or custom terms — the exact due date, with weekends explained.
Late Fee Calculator
Flat, one-time percent or monthly percent pro-rated by days overdue — the fee and the new total.
Early Payment Discount Calculator
2/10 Net 30 in plain numbers: both deadlines, the savings, and the annualized cost of skipping it.
Invoice Deposit Calculator
Project total × deposit percentage — the deposit to invoice now and the balance on completion.
Billable Hours Calculator
Hours and minutes to decimal hours, times your rate — the exact number for the invoice line.
Taxes & pricing
Self-Employed Tax Calculator
The 2026 federal estimate for freelancers: SE tax, income tax, quarterly payments, and what to set aside from every invoice.
Sales Tax Calculator
Add tax to a price — or extract it from a tax-inclusive total, the direction everyone gets wrong.
Markup & Margin Calculator
Cost plus one slider — price, profit and both percentages, with the conversion table worth memorizing.
Turn the numbers into an invoice — free — no signup, no watermark, and your PDF is ready in seconds.
Working with a number these don't cover yet? Tell us on the contact page and we'll build that calculator next.