Mortgage Repayment Calculator
ANA›Life Services Authority›National Calculator Authority›Mortgage Repayment Calculator
.calc-container { max-width: 640px; margin: 2rem 0; padding: 1.5rem; background: #fff; border: 1px solid #ddd; border-radius: 8px; box-shadow: 0 1px 3px rgba(0,0,0,0.06); font-family: system-ui, -apple-system, sans-serif; } .calc-container h3 { font-family: Georgia, serif; font-size: 1.15rem; color: #1a1a1a; margin-bottom: 1rem; padding-bottom: 0.5rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-row { display: flex; align-items: center; gap: 0.75rem; margin-bottom: 0.75rem; flex-wrap: wrap; } .calc-row label { min-width: 160px; font-size: 0.9rem; color: #333; font-weight: 500; } .calc-row input[type="number"], .calc-row select { flex: 1; min-width: 120px; max-width: 200px; padding: 0.5rem 0.6rem; border: 1px solid #ccc; border-radius: 4px; font-size: 0.9rem; font-family: system-ui, sans-serif; color: #1a1a1a; background: #fafaf8; } .calc-row input:focus, .calc-row select:focus { outline: none; border-color: var(--ac, #3d5a80); box-shadow: 0 0 0 2px rgba(26,74,138,0.12); } .calc-row .unit { font-size: 0.82rem; color: #888; min-width: 30px; } .calc-btn { display: inline-block; margin-top: 0.5rem; padding: 0.55rem 1.5rem; background: var(--ac, #3d5a80); color: #fff; border: none; border-radius: 4px; font-size: 0.9rem; font-weight: 600; cursor: pointer; font-family: system-ui, sans-serif; } .calc-btn:hover { opacity: 0.9; } .calc-result { margin-top: 1.25rem; padding: 1rem 1.25rem; background: #f0f6fc; border-left: 3px solid var(--ac, #3d5a80); border-radius: 0 6px 6px 0; display: none; } .calc-result.visible { display: block; } .calc-result-label { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.06em; color: #666; margin-bottom: 0.25rem; } .calc-result-value { font-size: 1.6rem; font-weight: 700; color: var(--ac, #3d5a80); } .calc-result-detail { font-size: 0.85rem; color: #555; margin-top: 0.5rem; line-height: 1.5; } .calc-note { margin-top: 1rem; font-size: 0.8rem; color: #888; font-style: italic; } .calc-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; margin-top: 0.75rem; } .calc-grid-item { padding: 0.6rem 0.8rem; background: #f8f9fa; border-radius: 4px; border: 1px solid #eee; } .calc-grid-item .label { font-size: 0.75rem; color: #888; text-transform: uppercase; letter-spacing: 0.04em; } .calc-grid-item .value { font-size: 1.1rem; font-weight: 600; color: #1a1a1a; } @media (max-width: 720px) { .calc-row { flex-direction: column; align-items: flex-start; gap: 0.3rem; } .calc-row label { min-width: auto; } .calc-row input[type="number"], .calc-row select { max-width: 100%; width: 100%; } .calc-grid { grid-template-columns: 1fr; } } .calc-chart { margin: 1rem 0; text-align: center; } .calc-chart svg { max-width: 100%; height: auto; } .calc-chart-legend { display: flex; flex-wrap: wrap; justify-content: center; gap: 0.6rem 1.2rem; margin-top: 0.6rem; font-size: 0.8rem; color: #555; } .calc-chart-legend span { display: inline-flex; align-items: center; gap: 0.3rem; } .calc-chart-legend i { display: inline-block; width: 10px; height: 10px; border-radius: 2px; font-style: normal; } .calc-related { max-width: 640px; margin: 2rem 0 1rem; padding: 1.25rem 1.5rem; background: #f8f9fa; border: 1px solid #e8e8e8; border-radius: 8px; } .calc-related h3 { font-family: Georgia, serif; font-size: 1rem; color: #1a1a1a; margin: 0 0 0.75rem; padding-bottom: 0.4rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-related-list { list-style: none; padding: 0; margin: 0 0 0.75rem; display: grid; grid-template-columns: 1fr 1fr; gap: 0.4rem 1.5rem; } .calc-related-list li a { font-size: 0.88rem; color: var(--ac, #3d5a80); text-decoration: none; } .calc-related-list li a:hover { text-decoration: underline; } .calc-browse-all { margin: 0.5rem 0 0; font-size: 0.9rem; font-weight: 600; } .calc-browse-all a { color: var(--ac, #3d5a80); text-decoration: none; } .calc-browse-all a:hover { text-decoration: underline; } @media (max-width: 720px) { .calc-related-list { grid-template-columns: 1fr; } }
Mortgage Repayment Calculator
Calculate your monthly mortgage repayments, total interest paid, and the full amortisation breakdown based on your loan details.
Loan Amount ($)
Annual Interest Rate (%)
Loan Term (Years)
Repayment Type
Principal & Interest Interest Only
Extra Monthly Repayment ($) (optional)
Calculate
function morCalc() { var resultDiv = document.getElementById('mor-result'); resultDiv.style.display = 'none'; resultDiv.innerHTML = '';
var principal = parseFloat(document.getElementById('mor-principal').value); var annualRate = parseFloat(document.getElementById('mor-rate').value); var termYears = parseFloat(document.getElementById('mor-term').value); var repayType = document.getElementById('mor-type').value; var extra = parseFloat(document.getElementById('mor-extra').value) || 0;
// --- Validation --- var errors = []; if (isNaN(principal) || principal 30) errors.push('Annual interest rate must be between 0.01% and 30%.'); if (isNaN(termYears) || termYears 50 || !Number.isInteger(termYears)) errors.push('Loan term must be a whole number between 1 and 50 years.'); if (extra 0) { resultDiv.style.display = 'block'; resultDiv.innerHTML = '' + errors.map(function(e){ return ''; }).join('') + ''; return; }
var r = annualRate / 100 / 12; // monthly interest rate var n = termYears * 12; // total number of payments
var monthlyPayment, totalInterest, totalPaid;
if (repayType === 'interest-only') { // Interest-only: monthly payment = P * r monthlyPayment = principal * r; totalInterest = monthlyPayment * n; totalPaid = totalInterest + principal;
var html = '### Results '; html += ''; html += 'Monthly Repayment (Interest Only)' + fmt(monthlyPayment) + ''; html += 'Total Interest Paid' + fmt(totalInterest) + ''; html += 'Total Amount Paid' + fmt(totalPaid) + ''; html += 'Principal Remaining at End' + fmt(principal) + ''; html += ''; html += 'Note: With interest-only loans, the full principal is still owed at the end of the term.
';
resultDiv.innerHTML = html; resultDiv.style.display = 'block'; return; }
// --- Principal & Interest --- // Standard amortisation formula: M = P * [r(1+r)^n] / [(1+r)^n - 1] var onePlusR_n = Math.pow(1 + r, n); monthlyPayment = principal * (r * onePlusR_n) / (onePlusR_n - 1);
// --- Amortisation with extra repayments --- var balance = principal; var totalInterestPaid = 0; var totalPaidActual = 0; var actualMonths = 0; var schedule = [];
for (var i = 1; i = balance) { payment = balance + interestCharge; principalCharge = balance; }
balance = balance - principalCharge - extra; if (balance '; html += 'Monthly Repayment' + fmt(monthlyPayment) + ''; if (extra > 0) { html += 'Monthly Repayment (incl. extra)' + fmt(monthlyPayment + extra) + ''; } html += 'Total Interest Paid' + fmt(totalInterestPaid) + ''; html += 'Total Amount Paid' + fmt(totalPaidActual) + ''; html += 'Loan Term' + termYears + ' years (' + n + ' months)'; if (extra > 0) { html += 'Actual Payoff Time' + Math.floor(actualMonths/12) + ' yrs ' + (actualMonths%12) + ' mths'; html += 'Interest Saved (extra repayments)' + fmt(savedInterest) + ''; html += 'Time Saved' + Math.floor(savedMonths/12) + ' yrs ' + (savedMonths%12) + ' mths'; } html += '';
// Amortisation schedule (collapsed) html += ''; html += 'View Amortisation Schedule'; html += ''; html += ''; html += 'MonthPaymentPrincipalInterestBalance'; for (var j = 0; j '; html += '' + row.month + ''; html += '' + fmt(row.payment) + ''; html += '' + fmt(row.principal) + ''; html += '' + fmt(row.interest) + ''; html += '' + fmt(row.balance) + ''; html += ''; } html += '';
resultDiv.innerHTML = html; resultDiv.style.display = 'block'; }
function fmt(val) { return '$' + val.toLocaleString('en-AU', {minimumFractionDigits: 2, maximumFractionDigits: 2}); }
#### Formula
Principal & Interest Monthly Repayment:
M = P × [r(1 + r)n] / [(1 + r)n − 1]
- M = Monthly repayment
- P = Principal loan amount
- r = Monthly interest rate = Annual rate ÷ 12
- n = Total number of monthly payments = Years × 12
Interest Only Monthly Repayment:
M = P × r
Total Interest Paid (no extra repayments):
Total Interest = (M × n) − P
#### Assumptions & References
- Reference: ASIC MoneySmart – Mortgage Calculator
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