Loan calculator with extra payments

Explore a fixed-rate loan, review its monthly amortization schedule, and compare extra principal payments with the same loan without extra payments. The starting numbers are an editable illustration, not a loan offer.

Calculation results

Last calculated inputs: principal $20,000.00, nominal APR 6%, contract term 60 months, extra payment $0.00 per month.

All amounts are nominal in the selected display currency, without an inflation adjustment.

Base monthly payment: $386.66
Planned monthly payment including extra: $386.66
Actual payoff month: 60 months
Total actual payments: $23,199.36
Total interest: $3,199.36
Interest saved vs. no extra payments: $0.00
Months saved vs. no extra payments: 0 months
Interest without extra payments: $3,199.36
Payoff month without extra payments: 60 months

Calculations keep unrounded monthly values. Amounts shown are rounded to two decimals, so displayed rows may differ slightly from displayed totals. The last payment is limited to the remaining principal and interest; actual lender rounding may differ.

Monthly amortization for the last calculation. Principal includes the actual extra payment; do not add the extra column to principal again.
Month	Opening balance	Interest	Total principal repaid	Actual extra principal	Actual payment	Closing balance
1	$20,000.00	$100.00	$286.66	$0.00	$386.66	$19,713.34
2	$19,713.34	$98.57	$288.09	$0.00	$386.66	$19,425.25
3	$19,425.25	$97.13	$289.53	$0.00	$386.66	$19,135.72
4	$19,135.72	$95.68	$290.98	$0.00	$386.66	$18,844.75
5	$18,844.75	$94.22	$292.43	$0.00	$386.66	$18,552.32
6	$18,552.32	$92.76	$293.89	$0.00	$386.66	$18,258.42
7	$18,258.42	$91.29	$295.36	$0.00	$386.66	$17,963.06
8	$17,963.06	$89.82	$296.84	$0.00	$386.66	$17,666.22
9	$17,666.22	$88.33	$298.32	$0.00	$386.66	$17,367.89
10	$17,367.89	$86.84	$299.82	$0.00	$386.66	$17,068.07
11	$17,068.07	$85.34	$301.32	$0.00	$386.66	$16,766.76
12	$16,766.76	$83.83	$302.82	$0.00	$386.66	$16,463.94
13	$16,463.94	$82.32	$304.34	$0.00	$386.66	$16,159.60
14	$16,159.60	$80.80	$305.86	$0.00	$386.66	$15,853.74
15	$15,853.74	$79.27	$307.39	$0.00	$386.66	$15,546.35
16	$15,546.35	$77.73	$308.92	$0.00	$386.66	$15,237.43
17	$15,237.43	$76.19	$310.47	$0.00	$386.66	$14,926.96
18	$14,926.96	$74.63	$312.02	$0.00	$386.66	$14,614.94
19	$14,614.94	$73.07	$313.58	$0.00	$386.66	$14,301.36
20	$14,301.36	$71.51	$315.15	$0.00	$386.66	$13,986.21
21	$13,986.21	$69.93	$316.72	$0.00	$386.66	$13,669.49
22	$13,669.49	$68.35	$318.31	$0.00	$386.66	$13,351.18
23	$13,351.18	$66.76	$319.90	$0.00	$386.66	$13,031.28
24	$13,031.28	$65.16	$321.50	$0.00	$386.66	$12,709.78
25	$12,709.78	$63.55	$323.11	$0.00	$386.66	$12,386.67
26	$12,386.67	$61.93	$324.72	$0.00	$386.66	$12,061.95
27	$12,061.95	$60.31	$326.35	$0.00	$386.66	$11,735.60
28	$11,735.60	$58.68	$327.98	$0.00	$386.66	$11,407.62
29	$11,407.62	$57.04	$329.62	$0.00	$386.66	$11,078.00
30	$11,078.00	$55.39	$331.27	$0.00	$386.66	$10,746.74
31	$10,746.74	$53.73	$332.92	$0.00	$386.66	$10,413.82
32	$10,413.82	$52.07	$334.59	$0.00	$386.66	$10,079.23
33	$10,079.23	$50.40	$336.26	$0.00	$386.66	$9,742.97
34	$9,742.97	$48.71	$337.94	$0.00	$386.66	$9,405.03
35	$9,405.03	$47.03	$339.63	$0.00	$386.66	$9,065.40
36	$9,065.40	$45.33	$341.33	$0.00	$386.66	$8,724.07
37	$8,724.07	$43.62	$343.04	$0.00	$386.66	$8,381.03
38	$8,381.03	$41.91	$344.75	$0.00	$386.66	$8,036.28
39	$8,036.28	$40.18	$346.47	$0.00	$386.66	$7,689.81
40	$7,689.81	$38.45	$348.21	$0.00	$386.66	$7,341.60
41	$7,341.60	$36.71	$349.95	$0.00	$386.66	$6,991.65
42	$6,991.65	$34.96	$351.70	$0.00	$386.66	$6,639.95
43	$6,639.95	$33.20	$353.46	$0.00	$386.66	$6,286.50
44	$6,286.50	$31.43	$355.22	$0.00	$386.66	$5,931.27
45	$5,931.27	$29.66	$357.00	$0.00	$386.66	$5,574.27
46	$5,574.27	$27.87	$358.78	$0.00	$386.66	$5,215.49
47	$5,215.49	$26.08	$360.58	$0.00	$386.66	$4,854.91
48	$4,854.91	$24.27	$362.38	$0.00	$386.66	$4,492.53
49	$4,492.53	$22.46	$364.19	$0.00	$386.66	$4,128.34
50	$4,128.34	$20.64	$366.01	$0.00	$386.66	$3,762.32
51	$3,762.32	$18.81	$367.84	$0.00	$386.66	$3,394.48
52	$3,394.48	$16.97	$369.68	$0.00	$386.66	$3,024.79
53	$3,024.79	$15.12	$371.53	$0.00	$386.66	$2,653.26
54	$2,653.26	$13.27	$373.39	$0.00	$386.66	$2,279.87
55	$2,279.87	$11.40	$375.26	$0.00	$386.66	$1,904.62
56	$1,904.62	$9.52	$377.13	$0.00	$386.66	$1,527.48
57	$1,527.48	$7.64	$379.02	$0.00	$386.66	$1,148.46
58	$1,148.46	$5.74	$380.91	$0.00	$386.66	$767.55
59	$767.55	$3.84	$382.82	$0.00	$386.66	$384.73
60	$384.73	$1.92	$384.73	$0.00	$386.66	$0.00

Results use the stated assumptions and model. They are educational, not financial advice or predictions.

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How this loan model works

Let L be principal, a the nominal APR as a decimal, n the number of months, and j = a / 12. The base monthly payment is M = L × j / (1 − (1 + j)^(−n)). At zero APR, M = L / n. This is a fixed-rate mathematical model, not a regulatory APR disclosure.

Each month interest is opening balance × j. The actual payment is the smaller of M plus your extra payment and the outstanding principal plus that month’s interest. Payment covers interest first, then principal. Only the extra amount actually paid appears in the extra principal column. The comparison uses the same principal, APR, and contract term with no extra payments.

Worked illustration: 1,200 principal, 0% APR, and 12 months gives a base payment of 100, total payments of 1,200, and zero interest. An extra 100 each month repays this loan in 6 months. With an extra 2,000, the first and only actual payment is 1,200, including 1,100 of extra principal.

Educational fixed-rate, monthly, no-fee model only; not financial advice, a prediction, or a loan quote. It excludes variable rates, prepayment penalties, lender fees, insurance, taxes, credit scoring, applications, and lender matching.

FAQ

Is this APR a loan offer or an effective annual rate?

No. You supply a fixed nominal annual rate, which this model divides by 12. Fees are excluded, so the result is not a regulatory APR disclosure, an effective annual yield, or a lender offer.

Can an extra payment exceed the remaining balance?

You can enter a larger planned extra payment, but the model limits the actual payment to the remaining principal plus that month’s interest. It never treats unused payment budget as principal repaid.

Why might the schedule differ from my lender’s statement?

This model keeps full precision between months and rounds only for display. A lender may round each payment, use different dates or interest conventions, or charge fees and penalties that are not included here.

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