Compare the initial interest-only payment with the later fully amortizing payment.
It keeps the property value, balance, cash amounts, rate convention, payment timing, and comparison horizon visible so the result can be checked against an actual quote, statement, budget, or contract.
Calculation structure
Follow the money through time
Interest-only payment = principal × nominal annual rate ÷ 12; the unchanged principal then amortizes over the remaining term.
Visual explanation
See which inputs change the result
Stage 1→Stage 2→Later stageRecalculate from the balance remaining at each changeInterest-only payment = principal × nominal annual rate ÷ 12; the unchanged principal then amortizes over the remaining term.
Read the estimate correctly
Use the result with its assumptions
On 120,000 at 6%, the interest-only payment is 600 per month. After a 12-month interest-only period, the unchanged 120,000 amortizes over the remaining 108 months.
The model assumes no principal payments during the interest-only period and a constant entered rate.
Quick guide
How to use this calculator
Enter the contractual or scenario values requested by each label.
Keep amounts in one currency and use the whole-period unit shown on each label.
Review every result with the stated exclusions.
Calculation method
Calculation method
Interest-only payment = principal × nominal annual rate ÷ 12; the unchanged principal then amortizes over the remaining term.
The engine retains calculation precision and rejects invalid or numerically unreliable schedules.
Worked example
Scenario example
On 120,000 at 6%, the interest-only payment is 600 per month. After a 12-month interest-only period, the unchanged 120,000 amortizes over the remaining 108 months.
Interest-only payment = principal × nominal annual rate ÷ 12; the unchanged principal then amortizes over the remaining term.
Supported inputs
Precision and limits
Visible limits
Amounts are capped at 1e12, entered rates at 1000%, periods at 1,200 months or 100 years, and fixed decimals at 12 places. A derived ARM rate above 1000% is rejected.
International scope
No jurisdiction, currency, tax, insurance, index path, lender rule, or legal interpretation is assumed.
Not a quotation
Results are mathematical scenarios based only on entered terms.
Specific assumptions
The model assumes no principal payments during the interest-only period and a constant entered rate.
