How this calculator works
Each month, interest is charged on the balance still owed: balance × annual rate ÷ 12. Your fixed payment covers that interest first, and whatever is left reduces the balance. Early on the balance is large, so most of the payment is interest; as the balance falls, the split shifts toward principal. That schedule of shrinking interest and growing principal is amortization.
Any extra principal you add goes straight to the balance, which lowers every future interest charge — that is why small extra payments early in a loan save so much. The last payment is just what is left.
Assumptions and tips
- Fixed rate, monthly payments, interest charged monthly on the remaining balance.
- Property tax, insurance, PMI and fees are not included — see the mortgage calculator for those.
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Loan amount | $300,000 |
| Interest rate (APR) | 6.5 % |
| Loan term | 30 years |
| Extra principal each month | $0 |
| First payment month | 2026-12-01 |
| Show schedule | Monthly (every payment) |
| Result | Value |
|---|---|
| Monthly payment | $1,896.20 |
| Total interest | $382,633 |
| Total of all payments | $682,633 |
| Number of payments | 360 payments |
| Payoff | Nov 2056 |
| Interest share of the first payment | 85.7 % |
Amortization schedule (monthly) (first 12 rows — the calculator shows all 360):
| Payment | Paid | Principal | Interest | Balance |
|---|---|---|---|---|
| 1 · Dec 2026 | $1,896.20 | $271.20 | $1,625.00 | $299,728.80 |
| 2 · Jan 2027 | $1,896.20 | $272.67 | $1,623.53 | $299,456.12 |
| 3 · Feb 2027 | $1,896.20 | $274.15 | $1,622.05 | $299,181.97 |
| 4 · Mar 2027 | $1,896.20 | $275.64 | $1,620.57 | $298,906.34 |
| 5 · Apr 2027 | $1,896.20 | $277.13 | $1,619.08 | $298,629.21 |
| 6 · May 2027 | $1,896.20 | $278.63 | $1,617.57 | $298,350.58 |
| 7 · Jun 2027 | $1,896.20 | $280.14 | $1,616.07 | $298,070.44 |
| 8 · Jul 2027 | $1,896.20 | $281.66 | $1,614.55 | $297,788.79 |
| 9 · Aug 2027 | $1,896.20 | $283.18 | $1,613.02 | $297,505.60 |
| 10 · Sep 2027 | $1,896.20 | $284.72 | $1,611.49 | $297,220.89 |
| 11 · Oct 2027 | $1,896.20 | $286.26 | $1,609.95 | $296,934.63 |
| 12 · Nov 2027 | $1,896.20 | $287.81 | $1,608.40 | $296,646.82 |
Step by step:
- Monthly rate r = 6.5% ÷ 12 = 0.54167%; n = 360 payments
- Payment = 300,000 × 0.005417 ÷ (1 − (1 + 0.005417)^−360) = $1,896.2
- Month 1 interest = $300,000 × 0.005417 = $1,625; principal = $271.2
- New balance = $299,728.8 — repeat each month until the balance is 0
Monthly payment and total interest on common loans
Calculated with this tool (no extra payments).
| Loan | Monthly payment | Total interest |
|---|---|---|
| $200,000 · 6.5% · 30 yr | $1,264.14 | $255,089 |
| $300,000 · 6.5% · 30 yr | $1,896.20 | $382,633 |
| $300,000 · 6% · 15 yr | $2,531.57 | $155,683 |
| $400,000 · 7% · 30 yr | $2,661.21 | $558,036 |
| $25,000 · 7% · 5 yr | $495.03 | $4,702 |
| $35,000 · 8% · 6 yr | $613.66 | $9,184 |
| $10,000 · 9% · 3 yr | $318.00 | $1,448 |
Common mistakes to avoid
- Assuming the interest share is constant — it is highest at the start and shrinks every month.
- Sending extra money without marking it “principal only”; some servicers apply it to the next payment instead.
Frequently asked questions
What is the payment on a $300,000 loan at 6.5% for 30 years?
$1,896.20 a month, with about $382,633 of interest over the full term.
Why is most of my early payment interest?
Interest is charged on the balance, which is highest at the start. On a 30-year loan at 6.5%, about 86% of the first payment is interest.
How much does $200 extra a month save?
On $300,000 at 6.5% for 30 years, about $122,000 of interest and roughly 7 years — use the extra-payment box to see your own numbers.
Is an amortization schedule the same for car loans?
Yes — any fixed-rate installment loan (mortgage, auto, personal) amortizes the same way.
Sources
Built and reviewed by Anirban Kundu, Creator & Editor · M.Sc Physics, 20 years teaching science