Loan Amortization Calculator and Schedule Generator
Enter your loan amount, annual interest rate, term, and any extra monthly payment. The calculator applies the standard amortization formula to derive your exact monthly payment, then simulates every month of the loan — showing how each payment splits between interest and principal, what you owe after each instalment, and how much time and money extra payments save you. The full month-by-month schedule is available in the API response.
Monthly payment
$396.02
60 payments
Total interest
$3,761.44
Total paid
$23,761.44
Balance over time
Full amortization schedule (60 months)
| Mo. | Payment | Interest | Principal | Balance |
|---|---|---|---|---|
| 1 | $396.03 | $116.67 | $279.36 | $19,720.64 |
| 2 | $396.03 | $115.04 | $280.99 | $19,439.66 |
| 3 | $396.03 | $113.40 | $282.63 | $19,157.03 |
| 4 | $396.02 | $111.75 | $284.27 | $18,872.76 |
| 5 | $396.02 | $110.09 | $285.93 | $18,586.82 |
| 6 | $396.02 | $108.42 | $287.60 | $18,299.22 |
| 7 | $396.03 | $106.75 | $289.28 | $18,009.94 |
| 8 | $396.03 | $105.06 | $290.97 | $17,718.98 |
| 9 | $396.02 | $103.36 | $292.66 | $17,426.31 |
| 10 | $396.02 | $101.65 | $294.37 | $17,131.94 |
| 11 | $396.03 | $99.94 | $296.09 | $16,835.86 |
| 12 | $396.02 | $98.21 | $297.81 | $16,538.04 |
| 13 | $396.02 | $96.47 | $299.55 | $16,238.49 |
| 14 | $396.02 | $94.72 | $301.30 | $15,937.19 |
| 15 | $396.03 | $92.97 | $303.06 | $15,634.13 |
| 16 | $396.02 | $91.20 | $304.82 | $15,329.31 |
| 17 | $396.02 | $89.42 | $306.60 | $15,022.70 |
| 18 | $396.02 | $87.63 | $308.39 | $14,714.31 |
| 19 | $396.02 | $85.83 | $310.19 | $14,404.12 |
| 20 | $396.02 | $84.02 | $312.00 | $14,092.12 |
| 21 | $396.02 | $82.20 | $313.82 | $13,778.30 |
| 22 | $396.02 | $80.37 | $315.65 | $13,462.65 |
| 23 | $396.02 | $78.53 | $317.49 | $13,145.16 |
| 24 | $396.02 | $76.68 | $319.34 | $12,825.82 |
| 25 | $396.03 | $74.82 | $321.21 | $12,504.61 |
| 26 | $396.02 | $72.94 | $323.08 | $12,181.53 |
| 27 | $396.03 | $71.06 | $324.97 | $11,856.56 |
| 28 | $396.02 | $69.16 | $326.86 | $11,529.70 |
| 29 | $396.03 | $67.26 | $328.77 | $11,200.94 |
| 30 | $396.03 | $65.34 | $330.69 | $10,870.25 |
| 31 | $396.02 | $63.41 | $332.61 | $10,537.64 |
| 32 | $396.02 | $61.47 | $334.55 | $10,203.08 |
| 33 | $396.03 | $59.52 | $336.51 | $9,866.58 |
| 34 | $396.03 | $57.56 | $338.47 | $9,528.11 |
| 35 | $396.02 | $55.58 | $340.44 | $9,187.66 |
| 36 | $396.02 | $53.59 | $342.43 | $8,845.23 |
| 37 | $396.03 | $51.60 | $344.43 | $8,500.81 |
| 38 | $396.03 | $49.59 | $346.44 | $8,154.37 |
| 39 | $396.03 | $47.57 | $348.46 | $7,805.92 |
| 40 | $396.02 | $45.53 | $350.49 | $7,455.43 |
| 41 | $396.02 | $43.49 | $352.53 | $7,102.89 |
| 42 | $396.02 | $41.43 | $354.59 | $6,748.30 |
| 43 | $396.03 | $39.37 | $356.66 | $6,391.64 |
| 44 | $396.02 | $37.28 | $358.74 | $6,032.90 |
| 45 | $396.02 | $35.19 | $360.83 | $5,672.07 |
| 46 | $396.03 | $33.09 | $362.94 | $5,309.13 |
| 47 | $396.02 | $30.97 | $365.05 | $4,944.08 |
| 48 | $396.02 | $28.84 | $367.18 | $4,576.90 |
| 49 | $396.03 | $26.70 | $369.33 | $4,207.57 |
| 50 | $396.02 | $24.54 | $371.48 | $3,836.09 |
| 51 | $396.03 | $22.38 | $373.65 | $3,462.44 |
| 52 | $396.03 | $20.20 | $375.83 | $3,086.62 |
| 53 | $396.03 | $18.01 | $378.02 | $2,708.60 |
| 54 | $396.02 | $15.80 | $380.22 | $2,328.38 |
| 55 | $396.02 | $13.58 | $382.44 | $1,945.93 |
| 56 | $396.02 | $11.35 | $384.67 | $1,561.26 |
| 57 | $396.03 | $9.11 | $386.92 | $1,174.34 |
| 58 | $396.02 | $6.85 | $389.17 | $785.17 |
| 59 | $396.02 | $4.58 | $391.44 | $393.73 |
| 60 | $396.03 | $2.30 | $393.73 | $0.00 |
How it works
Each monthly payment is split using the standard amortization formula: monthly payment = loan × (r / (1 − (1 + r)^−n)), where r is the monthly rate and n is the term in months. From that fixed payment, the interest portion each month equals your remaining balance × the monthly rate, and the rest reduces principal. Because the balance shrinks month after month, interest falls and principal rises — which is why early payments are almost entirely interest while later ones are mostly principal.
Extra monthly payments go entirely to principal the moment they land, shrinking the balance that interest is charged against. Even a modest extra payment compounds over time: the reduced balance means less interest next month, so principal falls faster the following month, and so on — a snowball effect that cuts both the total interest paid and the number of months needed to pay off the loan.
The API response returns the complete monthly schedule, not just summary figures. Each row carries the month number, actual payment (including any overpayment or final clamp), interest charged, principal paid, and remaining balance. This makes the endpoint suitable for embedding live repayment tables in fintech apps, mortgage dashboards, and consumer calculators that need raw figures rather than pre-formatted HTML.
Frequently asked questions
Can I use this for any loan type?+
Yes — for any fixed-rate, fully amortizing loan: personal loans, auto loans, mortgages, student loans, and home equity loans all use this formula. It does not model adjustable-rate mortgages (where the rate changes periodically), interest-only loans, balloon loans, or loans with fees rolled in. For those, the payment and schedule shown here will differ from your actual statement.
Why does my lender's schedule differ slightly?+
Two common reasons: day-count conventions and payment rounding. Most lenders calculate daily or exact-day interest (actual/365 or 30/360) rather than a flat monthly rate, which shifts a few cents per month. Many also round the monthly payment up to the nearest cent, creating a slightly larger final payment that clears the residual. These differences are cosmetic over a long loan — typically under a few dollars in total interest — but they explain why your lender's schedule doesn't match ours to the penny.
Is the API available?+
Yes. POST to /api/v1/tools/loan-amortization-calculator with a JSON body containing loanAmount, annualRatePct, termMonths, and extraMonthly. The response includes the full monthly schedule — every row with payment, interest, principal, and balance — along with summary figures for both the base scenario and the with-extra scenario. This makes it straightforward to power your own repayment table, savings widget, or payoff projection without doing the maths client-side.