What's inside
- Extra payments every way people actually make them: a monthly extra (from any payment), a once-a-year extra (bonus or tax refund month), a one-time lump sum, and a biweekly-style option (13 payments a year)
- Full schedule up to 40 years: interest, principal, extra applied and balance for every payment, with the standard schedule alongside
- Type what you actually paid in any month and everything after it updates
- Plan tab: number of payments, mortgage-free date, total interest both ways, interest and time saved, and a balance chart
- Goal: enter the year you want to be mortgage-free and see the monthly extra that gets you there
- Works for a new loan or one you're partway through: enter today's balance and payments left, or the exact payment from your statement
- Sample file: $320,000 at 6.75% over 30 years with $200 a month extra and $1,500 every April. Paid off 9 years 5 months sooner, $154,352.86 less interest
Checked, not just designed: 6,261 formulas, zero errors, and the schedule matches an independent month-by-month simulation in 6 scenarios: same balance every month and the same total interest to the cent.
Works in Excel and Google Sheets. Not financial advice. Principal and interest only (escrow not included); lenders that compute interest daily will differ slightly.
Try the free version first
The free online calculator uses the same model for a quick answer. The spreadsheet adds tracking, history and the full views.