Amortization Calculator
See where every payment actually goes across the life of a loan — and how long it takes before more of your money is buying equity than buying the lender's interest.
Amortization Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Results are a model, not a quotation — an institution's own figures govern.
- Every input is an assumption; change one and the answer changes with it.
- Rounding is applied only at the display layer, so totals may differ by a cent from a statement that rounds each line.
In short: Amortisation splits each level payment between interest on the outstanding balance and principal reduction. On $240,000 at 6.25% over 30 years the payment is $1,477.72, but month one is $1,250.00 interest against $227.72 principal, and principal does not overtake interest until month 228.
Formula
M = the level payment · i = monthly rate. The payment never changes; the split between the two columns does, every single month.
Worked Example
- Find the level payment. $240,000 at 6.25% over 360 months = $1,477.72.
- Charge month one's interest. $240,000 × 0.0052083 = $1,250.00.
- Apply the remainder to principal. $1,477.72 − $1,250.00 = $227.72, leaving $239,772.28.
- Repeat on the new balance. Month two charges interest on $239,772.28, so slightly less interest and slightly more principal — every month thereafter.
- Find the crossover. Principal first exceeds interest at month 228, in year 19 of 30.
Analyst's note. At the exact midpoint of this loan — the end of year 15 — you have repaid 28.2% of the principal but paid 67.9% of all the interest the loan will ever charge. That asymmetry is the single most misunderstood feature of amortising debt, and it is why refinancing late in a term rarely recovers what borrowers expect.
Strengths & Limits Of This Model
Where this engine is strong
- Runs entirely in your browser — no figure you type is transmitted or stored.
- Shows the full working, so every number can be traced and challenged.
- Free, unmetered and free of affiliate incentives.
Where it stops
- Generalised assumptions cannot capture every individual circumstance.
- Jurisdiction-specific rules and mid-year changes may not be reflected.
- A model output is not a substitute for a professional review of your position.
Practical Use Cases
Judging whether to refinance
Compare the interest remaining on your current schedule, not the interest already paid, against the new loan's total. Resetting to a fresh 30-year term restarts the front-loaded interest curve. Price the switch with the Refinance Calculator including the closing costs.
Planning around a known sale date
Read the balance at the year you expect to sell or repay. That figure, not the original loan amount, is what the transaction must clear. For property, pair it with the Home Equity Calculator to see the net position after the outstanding balance.
Quantifying what an overpayment removes
Because interest is charged on the balance, a payment made in year 2 removes far more future interest than the same payment in year 20. Model the effect on total interest with the Extra Payment Calculator before committing to a monthly overpayment.
Methodology & Editorial Standards
The engine simulates the schedule month by month rather than using closed-form balance formulas, so every reported figure — the annual splits, the running totals and the crossover month — comes from the same single pass over the real balance path. The final payment is trimmed to clear any residual balance exactly, which is why total interest is not simply payment × term. The crossover is reported as the first month in which the principal component strictly exceeds the interest component. The engine implements the standard published formula for this calculation. Inputs are validated for domain and sign before evaluation, and any undefined case returns an em-dash rather than a spurious value.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Amortization Calculator — 20 Expert FAQs
20 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
What does amortisation actually mean?
It is the process of retiring a debt through level payments, each of which is split between interest on the current balance and a reduction of that balance. The payment is constant; the split shifts toward principal every month as the balance falls.
Why is my early payment almost all interest?
Because interest is charged on the outstanding balance, which is at its maximum at the start. On $240,000 at 6.25%, month one charges $1,250.00 of interest and only $227.72 reaches the principal. That is arithmetic, not a fee.
When does principal overtake interest?
On these terms, month 228 — year 19 of a 30-year loan. The crossover point depends on the rate and term: higher rates and longer terms push it later. This engine calculates the exact month for your inputs.
How much of the loan is repaid at the halfway point?
Far less than half. At the end of year 15 of 30 you have repaid 28.2% of the principal while paying 67.9% of the total interest. Halfway through the term is nowhere near halfway through the debt.
Does the payment ever change?
Not on a fixed-rate loan. What changes is its composition. On an adjustable-rate loan the payment is recalculated at each reset against the new rate and the remaining term, which restarts a portion of the front-loading.
Why is total interest not simply payment times term?
Because the last payment is trimmed to clear the residual balance exactly rather than overshooting. The difference is small — a few dollars — but this engine reports the schedule's true total rather than the multiplied approximation.
How do extra payments change the schedule?
An extra payment reduces the balance immediately, so every subsequent interest charge is smaller and more of each future payment attacks principal. The term shortens; the payment does not. Early extra payments are worth several times late ones.
Should I refinance if I am well into my term?
Be careful. Late in a term most of the payment is already principal, so a new loan at a lower rate but a fresh 30-year clock can increase your total interest despite the better headline rate. Compare remaining interest, not rates.
What is negative amortisation?
When the payment is smaller than the interest accruing, so the shortfall is added to the balance and the debt grows. It appears in some interest-only, graduated-payment and deferred structures, and it is the opposite of the schedule modelled here.
Does this work for car loans and personal loans?
Yes — the mathematics is identical for any fixed-rate, fully amortising loan. Only the scale and term differ. Shorter terms have a much earlier crossover, which is why a five-year car loan feels less front-loaded than a mortgage.
What balance will I owe when I sell?
Enter the year you expect to sell and read the balance at the end of that year. That figure is what the sale must clear before any equity is released, along with selling costs and any second charge on the property.
Why does a higher rate delay the crossover?
Because a higher rate means a larger share of every payment is consumed by interest, so the balance falls more slowly, so the interest charge stays high for longer. Rate affects the shape of the schedule, not just its total.
Does the inspect-year box accept any year?
Any year within the term. If you enter a year beyond the term the engine clamps to the final year rather than reporting figures for a loan that has already been repaid.
Is interest calculated daily or monthly here?
Monthly, on the balance outstanding at the start of each period, which is the standard convention for amortising instalment loans. Lenders using a daily accrual will differ by a small amount depending on the day of the month you pay.
Can I see the full month-by-month table?
This engine reports the annual view plus any year you inspect, which is what most decisions require. For a full month-by-month schedule with running totals, use the Loan Amortization Calculator in the mortgage category.
Is this amortization calculator free to use?
Yes. It is free, requires no account, and has no usage limits. ApexConverter is funded by contextual advertising, never by selling user data.
Is my data sent to a server?
No. The engine runs as Vanilla JavaScript inside your browser under our Zero-Server Client-Side Execution model. Your figures are computed locally and are never transmitted, logged, or stored.
How accurate is this calculator?
It applies the standard closed-form formula in IEEE-754 double precision, rounding only at the display layer. The engine is reconciled against an independent reference implementation before release.
Does it work on mobile?
Yes. The interface is mobile-first with numeric keypad hints and is tested down to a 320-pixel viewport with no horizontal scrolling.
Can I use it offline?
Largely, yes. Because computation is client-side, the page continues to calculate without a network connection once it has loaded.