Mortgage Repayment Calculator — Break the Loan Free, Years Early
Add an extra amount to your monthly mortgage payment and instantly see your new payoff date, how many years you shave off, and how much interest you save.
Your loan + extra payment
Advanced options
Optional extras — leave them at 0 for the standard calculation. They take effect when you press Calculate.
🔒 All calculations happen in your browser — no data leaves your device.
Your early payoff
Your amortization schedule
Every payment in the plan, in order — switch between the schedule with your extra payments and the original schedule. In biweekly mode the rows are the two-weekly payments, dated as they fall.
- On the default loan — $200,000 at 6% with 30 years left — adding $200 a month pays the loan off 9 years early and saves $79,800.51 in interest: 252 months instead of 360.
- The new monthly payment is $1,399.10 instead of $1,199.10, and total interest falls from $231,676.38 to $151,875.87 — every extra dollar goes straight to principal.
- Early extra payments save the most: an extra $200 a month in year 1 alone removes roughly $2,400 of future interest, because each extra dollar kills the interest it would have carried for decades.
Watch your timeline shrink
The gray bar is your original term — the coral bar is your new term with the extra payment.
Keep exploring
Three companion tools for the full loan picture.
How it works
Three steps from your balance to a new payoff date.
Enter your loan
Type the remaining balance, the fixed interest rate, and the years left on the term.
Add an extra payment
Choose a monthly amount to put toward principal on top of the normal payment — or add a yearly extra or a one-off lump sum under Advanced options.
See the savings
Get the new payoff date, years shaved off, and total interest saved — updated as you type.
The math behind early repayment
Each month, your payment first covers the month’s interest, and the rest reduces the balance. An extra payment goes entirely to principal, which shrinks next month’s interest — a compounding effect. The calculator amortizes the loan month by month until the balance reaches zero:
Two schedules are built — one with the normal payment, one with the extra — and the difference in total interest is your interest saved. The payoff date is counted forward from your start date — today by default; you can set the start month and year under Advanced options.
Three more levers live under Advanced options. Biweekly mode pays half the monthly payment every two weeks — the 26 half-payments add up to a 13th monthly payment, which on the default loan alone, with no other extras, saves $49,624.01 and clears the loan in 294 months instead of 360. The annual overpayment cap models lender limits such as the 10%-of-balance allowance common on UK fixed-rate deals: extras above each year’s allowance are assumed not paid, so a $3,000 monthly extra with a 10% cap has $265,329.55 of extras held back over the life of the loan and still saves $175,200.39. And the extra payment itself can be entered as a percentage of the monthly payment — 10% on the default loan is $119.91 a month, and saves $56,296.32.
Worked examples:
| Inputs | Result |
|---|---|
| $200,000 at 6%, 30 yrs, extra $200/mo | Paid off in 252 months, interest saved $79,800.51, ~9 years early |
| $150,000 at 4%, 15 yrs, no extra | 180 months, total interest $49,715.74, $1,109.53/month |
| $100,000 at 5%, 10 yrs, extra $500/mo | Paid off in 75 months, interest saved $10,703.93, 3.75 years early |
| $50,000 at 6%, 20 yrs, extra $100,000/mo | Paid off in 1 month (edge case: $250.00 interest) |
Go deeper
The details that separate a rough guess from a trustworthy number.
Why do small extra payments save so much interest?
Early in a mortgage, most of your payment is interest. Extra principal paid now removes interest from every future month:
- On a $200,000 loan at 6%, an extra $200/month in year 1 alone saves roughly $2,400 of future interest.
- The effect compounds: each extra dollar kills the interest that dollar would have carried for decades.
- That is why $200 extra per month can erase 9 years and nearly $80,000 of interest on a 30-year loan.
- Late extra payments help far less — the same $200 in year 20 saves only a fraction.
Rule of thumb: the earlier the extra payment, the more it is worth.
What should I check before making extra payments?
Extra payments are not free of fine print:
- Prepayment penalties — some mortgages charge a fee for paying early; check your loan terms first.
- Higher-interest debt — paying down a 19% credit card beats extra payments on a 6% mortgage.
- Emergency fund — keep 3–6 months of expenses liquid before locking cash into the loan.
- Opportunity cost — investing the extra money can beat the mortgage rate over long horizons, with more risk.
This calculator assumes no penalty and that 100% of the extra goes to principal.
What is an annual overpayment cap — and the UK 10% rule?
Many UK fixed-rate mortgages limit penalty-free overpayments to a share of the balance each year — 10% is the most common allowance — and charge an early repayment charge (ERC) on anything above it:
- The allowance is usually measured against the balance at the start of each year of the deal.
- Monthly extras, yearly extras and lump sums all count toward the same allowance.
- Set the cap under Advanced options and this calculator will not assume extras above each year’s allowance — the schedule then shows what the capped plan really saves.
- When the fixed deal ends, the cap normally disappears — check your lender’s wording, because allowances and measurement dates vary.
If your loan has no such limit, leave the cap at 0 and every extra dollar is applied in full.
Reading your amortization schedule, row by row
The schedule this calculator builds is the loan’s whole life in rows: one row per month, and every row splits that month’s payment into interest and principal. Once you can read one row, you can read the whole loan.
Each row has four numbers that matter. Interest is the balance at the start of the month times the monthly rate, so on a $200,000 loan at 6%, the first month charges $200,000 times 0.06 divided by 12, which is $1,000.00 of interest. Principal is whatever is left of the payment after interest, so the first payment of $1,199.10 puts only $199.10 against the balance. Payment is the fixed monthly amount plus any extra you added, and balance is what you still owe after that row. The payment never changes on a fixed-rate loan, but the split inside it changes every single month, because the balance falls and interest is charged on the balance.
| Month | Interest | Principal | Balance after payment |
|---|---|---|---|
| 1 | $1,000.00 | $199.10 | $199,800.90 |
| 12 | $988.77 | $210.33 | $197,543.98 |
| 60 (year 5) | $931.88 | $267.22 | $186,108.71 |
| 120 (year 10) | $838.66 | $360.44 | $167,371.45 |
| 240 (year 20) | $543.31 | $655.79 | $108,007.17 |
| 360 (year 30) | $5.97 | $1,193.14 | $0.00 |
Read the table down the balance column and the slow start becomes concrete. After five years of $1,199.10 payments, you still owe $186,108.71, having repaid only $13,891.29 of principal, because the first year alone charges $11,933.19 of interest against $2,456.02 of principal. After ten years you owe $167,371.45. After twenty years, two thirds of the way through the loan, you still owe $108,007.17, more than half the original balance. The crossover, where principal first exceeds interest in a single payment, arrives late, and the final year is almost all principal: the last twelve payments charge $456.93 of interest in total against $13,932.29 of principal. That shape is not a flaw in the loan, it is what interest on a shrinking balance looks like, and it is exactly why extra payments made early are worth so much more than the same money sent late.
When you add an extra payment, the schedule changes in a specific way that is worth watching in the tool: the extra goes entirely to principal in the month you pay it, so the next row’s interest is charged on a smaller balance, and every row after that shifts. The payment column does not change, the finish date does. Compare the balance column with and without the extra at the same month, month 60 for example, where $200 extra a month leaves $172,154.71 owed instead of $186,108.71, and the gap between the two balances is the interest that will never be charged.
Monthly extra, yearly lump sum, or biweekly: three ways to pay extra
Same loan, $200,000 at 6% over 30 years, payment $1,199.10, total interest $231,676.38 with no extras. The three plans below differ only in when the extra money arrives.
| Plan | Extra per year | Months to clear | Total interest | Interest saved |
|---|---|---|---|---|
| No extra | $0 | 360 | $231,676.38 | — |
| $200 extra every month | $2,400 | 252 | $151,875.87 | $79,800.51 |
| $2,400 lump sum at each year end | $2,400 | 254 | $154,626.23 | $77,050.15 |
| Biweekly: a 13th monthly payment a year | $1,199.10 | 295 | $182,566.14 | $49,110.24 |
The monthly extra wins, but only just: $79,800.51 saved against $77,050.15 for the yearly lump sum, a difference of $2,750.36 and two months, on the same $2,400 a year. The reason is timing alone. Monthly extras retire principal eleven times before the year-end lump sum arrives at all, and each early retirement cancels interest in every month that follows. The lump sum is still an excellent plan, and for anyone whose extra money arrives once a year, as a bonus or a tax refund, it is the realistic one: sending it when it arrives beats waiting to dribble it out monthly. The biweekly plan in this table is modelled as one extra monthly payment spread across the year, half the yearly extra of the other two plans, which is why it saves less. Its real-world form is half the monthly payment every two weeks, 26 half-payments making 13 monthly payments a year, and its advantage is discipline rather than arithmetic: the extra happens automatically, without a monthly decision.
Timing matters even for a single lump sum, and the same $5,000 proves it. Sent with the first payment, it saves $23,303.70 of interest and clears the loan in 337 months. Sent at month 120, it saves $11,044.16 and clears it in 347 months. Sent at month 240, it saves $3,950.25 and clears it in 353 months. The money is identical, the loan is identical, and the only difference is how many interest-bearing months remain after it lands. That is the whole case for paying extra early, and it is also the reason to check the fine print first: this calculator assumes every extra dollar goes to principal with no prepayment penalty, and the guide above lists the checks, penalties, higher-rate debt, and the emergency fund, that come before any extra payment plan.
The crossover: when principal passes interest
On a $300,000 loan at 6 percent, the principal share passes the interest share around year eighteen. Before that, most of each payment is interest; after it, most is principal. The schedule makes the crossover visible, and it is the reason extra payments early matter most.
Escrow is not part of the split
Taxes and insurance collected with the payment are escrow items, not principal or interest. Extra principal payments do not reduce them, and the schedule split covers principal and interest only.
Frequently asked questions
Quick answers about this mortgage repayment calculator.
How do I calculate paying off my mortgage early?
Build two amortization schedules — one with your normal payment, one adding the extra amount to principal each month — and compare the months to zero and total interest. For example, $200,000 at 6% over 30 years with an extra $200/month finishes in 252 months and saves $79,800.51 of interest.
How much extra should I pay on my mortgage each month?
Even $100–$200 per month makes a large difference on a 30-year loan, because early extra principal removes interest from every future month. Try a few amounts above and compare the “Interest saved” figure — then pick the largest amount that still leaves your emergency fund intact.
Is it better to make extra payments or a lump sum?
Mathematically, the same total paid earlier always wins: a lump sum today beats the same dollars spread over the year, because it removes interest sooner. Monthly extra payments are simply the practical version for a budget. Both are modelled here — add a one-time lump sum and the month you pay it, or a yearly extra, under Advanced options.
Do extra mortgage payments go to principal?
Usually yes, once the current month’s interest is covered — but confirm with your lender, since some apply extra money to future payments instead. This calculator assumes 100% of the extra reduces principal.
Can extra payments hurt my mortgage?
Rarely, but check two things: prepayment penalties (some loans charge for early payoff) and whether you are diverting money from higher-interest debt or an emergency fund. Within those limits, extra principal payments only reduce interest. If your lender caps penalty-free overpayments — many UK fixed-rate deals allow 10% of the balance a year — set that cap under Advanced options and the plan will stay inside it.
What is the difference between this and a mortgage calculator?
A mortgage calculator finds your normal monthly payment from a price, deposit, rate, and term. This repayment calculator starts from your existing balance and focuses on extra payments: the new payoff date, years shaved off, and interest saved.
How do I read the amortization schedule on this calculator?
Each row is one month: interest is the opening balance times the monthly rate, principal is the rest of the payment, and balance is what remains. On a $200,000 loan at 6%, month 1 charges $1,000.00 of interest and $199.10 of principal, month 120 charges $838.66 and $360.44, and month 360 charges $5.97 and $1,193.14. After 5 years you still owe $186,108.71, and after 20 years $108,007.17, because early payments are mostly interest on a large balance.
Is a lump sum once a year as good as a monthly extra payment?
Nearly, but not quite. On a $200,000 loan at 6% over 30 years, $200 extra every month saves $79,800.51 and clears the loan in 252 months, while a $2,400 lump sum at each year end saves $77,050.15 and clears it in 254 months, a difference of $2,750.36. Monthly money retires principal earlier and cancels more future interest. A lump sum sent the day it arrives still beats the same money sent late: $5,000 at month 1 saves $23,303.70, but only $3,950.25 at month 240.
Why is my first payment almost all interest?
Because interest is charged on the full balance. On $300,000 at 6 percent, month one interest is $1,500 of a $1,799 payment, leaving $299 of principal. The interest share falls as the balance falls.
Does the payment change as the balance falls?
No, on a fixed mortgage the scheduled payment stays the same and the term shortens when extras are paid. Recasting, re-amortising at the lower balance for a fee, is what lowers the payment.
What is the UK 10 percent overpayment rule?
Most UK fixed deals allow overpaying up to 10 percent of the balance a year without charge. Above that, early-repayment charges may apply, so check the offer terms before paying a large lump sum.
Related guides
Extra-payment plans compared, and the schedule read row by row.
Mortgage Extra Payments vs Lump Sum
Monthly, yearly, and biweekly plans on the same loan, with the savings counted.
📉Reading Your Amortization Schedule
Interest, principal, balance milestones, and the late crossover.
📖How Mortgage Repayments Are Calculated: Principal, Interest, and Extra Repayments
Principal and interest, month by month: the formula, the schedule, and the three ways to pay extra.
Related calculators
More ways to plan the loan.
Disclaimer
This calculator is for information and planning only — not financial advice. It assumes a fixed interest rate, extra payments applied 100% to principal (monthly, yearly, or one-off lump sums, optionally limited by the annual overpayment cap you set), and no prepayment penalties, taxes, insurance, or fees. Real loans vary by lender and terms — check your mortgage agreement for prepayment rules and speak to a qualified adviser before changing your payments.