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Interest-Only Mortgage Calculator

Shows the payment shock at the end of the interest-only period: the low payment while only interest is due, the higher one once the whole principal has to be repaid over the years that are left, and the exact size of the jump. Puts the lifetime interest side by side with a fully amortising loan of the same rate and term.

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Interest-Only Mortgage Calculator works straight from this page — free, instant, nothing to install. It covers the low payment while only interest is due, the higher one once the whole principal has to be repaid over the years that are left, and the exact size of the jump. Puts the lifetime interest side by side with a fully amortising loan of the same rate and term — adjust any of them and the result follows immediately.

How to use it

  1. Open the tool — no signup or install needed.
  2. Enter your input or adjust the available options.
  3. Get your result instantly, then copy or download it.

Frequently asked questions

What does Interest-Only Mortgage Calculator do?

Shows the payment shock at the end of the interest-only period: the low payment while only interest is due, the higher one once the whole principal has to be repaid over the years that are left, and the exact size of the jump. Puts the lifetime interest side by side with a fully amortising loan of the same rate and term.

What does it take into account?

It factors in the low payment while only interest is due, the higher one once the whole principal has to be repaid over the years that are left, and the exact size of the jump. Puts the lifetime interest side by side with a fully amortising loan of the same rate and term. Change any of them and the output follows immediately.

When would I actually use this?

Before making an offer: what the bank will lend, what the purchase costs on top of the price, and how much deposit closes the gap.

What is the most common mistake?

Budgeting for the price and forgetting the acquisition costs. Notary fees, transfer duty and registration add between 2% and 15% depending on the country — enough to sink an offer.

How is Interest-Only Mortgage Calculator different from Mortgage Comparison Calculator?

They sit next to each other but answer different questions: Mortgage Comparison Calculator is the one to open when you need it to compare two mortgages — payment, total interest and total cost — to see which term and rate wins. Pick whichever matches what you're starting from — both are free.

Is there a tool for the next step?

PMI calculator (private mortgage insurance) is the closest one after this: Private mortgage insurance is charged when you put down less than 20%. From the price, down payment, term and rate the calculator finds your loan-to-value, estimates the annual PMI rate (or uses yours), and shows the monthly PMI, when it should drop off at 78% LTV, and the total PMI you'll pay until then.

What else is worth having open alongside it?

Reverse mortgage calculator (HECM estimate) and ARM mortgage calculator — they come up in the same task often enough to be worth a second tab.

Where do the figures come from?

Fee scales and duty rates are published per country and per region, and they change with each finance act. Lending limits also depend on the bank's own policy, not only on the regulator's debt-to-income cap.

Further reading

All guides →
ExplainerInterest-Only Mortgages: What You Are DeferringTen interest-only years on a $300,000 loan at 6 percent cost $180,000 and repay nothing. When amortisation starts the payment jumps from $1,500.00 to $2,149.29 — 43.3 percent overnight — and the loan ends up $48,315.79 dearer than the repayment version.ExplainerAdjustable-Rate Mortgages and the Caps That Bound ThemA 5.00 percent start with 2/2/5 caps can legally reach 10.00 percent and a payment of $2,484.14 — 54.3 percent above where it began. That worst case is computable before you sign, and it is the only number that should decide the choice.ComparisonComparing Two Mortgage Offers ProperlyThe rate is not the comparison. Over a five-year holding period the 6.25 percent offer with $2,000 of fees beats the 5.875 percent offer with $12,000 by $2,485.73; the crossover falls at month 80, not at the month 103 the simple payback suggests.ExplainerMortgage Points: When Buying Down the Rate Actually PaysOne point on a $300,000 loan costs $3,000 and saves $47.93 a month. The naive break-even is 63 months; discounted at 4 percent it is 71. And the number that decides it is not either of those — it is how long you keep the loan.ExplainerWhat Is Loan-to-Value (LTV), and Which Bands Actually Change AnythingLoan divided by the lower of price and appraised value. The bands at 80, 90 and 95 percent are where pricing steps — and a valuation that comes in low moves you across one without you touching the deposit.ExplainerHome Equity Is Not One NumberValue minus debt gives $139,167. After the costs of selling it is $111,867. What a lender will actually let you borrow against it is $55,167. Same house, same day, three answers — and the third is the one that governs.