Car Loan Calculator

"; return; } // Taxable base: price minus trade-in (common), then add tax const taxableBase = Math.max(price - trade, 0); const taxAmount = taxableBase * (taxRate/100); const netVehicleCost = price + taxAmount + feesUpfront; // Amount financed: net cost minus down payment minus trade-in + financed fees let financed = Math.max(netVehicleCost - down - trade, 0) + feesFinanced; // Periods & rates const periods = Math.round(termYears * payFreq); const ratePerComp = rateNominal / comp; // Convert nominal with compounding to effective per payment period const effAnnual = Math.pow(1 + ratePerComp, comp) - 1; const ratePerPeriod = Math.pow(1 + effAnnual, 1/payFreq) - 1; // Payment (without extras/insurance) const basePayment = financed * ratePerPeriod / (1 - Math.pow(1 + ratePerPeriod, -periods)); const paymentWithExtras = basePayment + extra + ins; // Build schedule schedule = []; let balance = financed; let totalInterest = 0, totalPrincipal = 0, totalPaid = 0, totalInsurance = 0, totalExtra = 0; for(let i=1; i<=periods && balance>0; i++){ const interest = balance * ratePerPeriod; let principal = basePayment - interest; // Apply extra payment entirely to principal principal += extra; if(principal > balance) principal = balance; balance -= principal; totalInterest += interest; totalPrincipal += principal; totalInsurance += ins; totalExtra += extra; totalPaid += (basePayment + extra + ins); schedule.push({ period: i, payment: r(basePayment + extra + ins), principal: r(principal), interest: r(interest), insurance: r(ins), extra: r(extra), balance: r(Math.max(balance,0)) }); } // Summary const totalVehicleOutlay = r(netVehicleCost); const totalPayments = r(totalPaid); const totalCost = r(totalVehicleOutlay + totalPayments - financed); // upfront + all periodic (interest+ins+extra+principal minus financed principal counted in vehicle outlay) const payoffPeriods = schedule.length; const payoffYears = r(payoffPeriods / payFreq); // Table const rows = schedule.map(rw => ` ${rw.period} ${fmt(rw.payment)} ${fmt(rw.principal)} ${fmt(rw.interest)} ${fmt(rw.insurance)} ${fmt(rw.extra)} ${fmt(rw.balance)} `).join(""); el('cl-results').innerHTML = ` ${rows}

Period	Payment	Principal	Interest	Insurance	Extra	Balance

`; drawChart(schedule); } function drawChart(data){ const ctx = document.getElementById('cl-chart').getContext('2d'); const labels = data.map(d => d.period); const principalData = data.map(d => d.principal); const interestData = data.map(d => d.interest); const balanceData = data.map(d => d.balance); if(chartInstance){ chartInstance.destroy(); } chartInstance = new Chart(ctx,{ type:'line', data:{ labels, datasets:[ {label:'Principal', data:principalData, borderColor:'#16a34a', backgroundColor:'transparent'}, {label:'Interest', data:interestData, borderColor:'#dc2626', backgroundColor:'transparent'}, {label:'Balance', data:balanceData, borderColor:'#2563eb', backgroundColor:'transparent'} ] }, options:{ responsive:true, interaction:{mode:'index', intersect:false}, plugins:{legend:{position:'bottom'}}, scales:{x:{title:{display:true,text:'Period'}}, y:{title:{display:true,text:'Amount'}}} } }); } function exportCSV(){ if(!schedule.length){ alert('No schedule to export.'); return; } let csv = "Period,Payment,Principal,Interest,Insurance,Extra,Balance\n"; schedule.forEach(r=>{ csv += `${r.period},${r.payment},${r.principal},${r.interest},${r.insurance},${r.extra},${r.balance}\n`; }); const blob = new Blob([csv], { type: 'text/csv;charset=utf-8;' }); const url = URL.createObjectURL(blob); const link = document.createElement("a"); link.href = url; link.download = "car_loan_schedule.csv"; document.body.appendChild(link); link.click(); document.body.removeChild(link); } function reset(){ ['cl-price','cl-down','cl-trade','cl-taxRate','cl-fees','cl-finFees','cl-rate','cl-term','cl-extra','cl-ins'].forEach(id => el(id).value = ''); el('cl-comp').value = '12'; el('cl-payFreq').value = '12'; el('cl-currency').value = 'USD'; el('cl-locale').value = 'en-US'; el('cl-round').value = '2'; el('cl-results').innerHTML = ''; if(chartInstance){ chartInstance.destroy(); chartInstance = null; } } return { calculate, exportCSV, reset }; })();