Investment Loan Monthly Payment Calculator
Use this calculator to find the exact fixed monthly payment for any investment loan, broker financing, or personal credit. Enter the loan amount, term in months, and nominal annual interest rate — you get the installment, total repayment, and interest paid instantly. The calculator uses the French amortization method (constant payment), the standard formula used by banks and brokers worldwide.
Monthly payment = Loan × [monthly_rate × (1 + monthly_rate)^months] ÷ [(1 + monthly_rate)^months − 1], where monthly_rate = Annual Rate ÷ 12. For example, a $10,000 loan at 8% annual rate over 24 months costs $452/month, repaying $10,855 total — $855 in interest.
When to use this calculator
- Calculate the monthly installment before signing a broker or bank loan
- Compare short vs. long loan terms to minimize interest paid
- Estimate monthly cash flow impact when financing an investment
- Check whether broker financing is cheaper than bank credit
- Plan repayments for margin loans or securities-backed credit
Example: $10,000 loan at 8% annual rate over 24 months
- Loan: $10,000 · Term: 24 months · Annual rate: 8% → monthly rate = 8% ÷ 12 = 0.6667%
- Monthly payment = $10,000 × 0.006667 × (1.006667)^24 ÷ ((1.006667)^24 − 1)
- Monthly payment = $10,000 × 0.006667 × 1.1729 ÷ 0.1729 = $452.27
- Total repaid: $452.27 × 24 = $10,854.55 — interest paid: $854.55 (8.55% of principal)
How it works
1 min readHow the monthly payment is calculated
This calculator uses the French amortization formula (also called constant-payment or level-payment loan), the universal standard for mortgages, personal loans, and investment financing:
monthly_rate = Annual Rate / 100 / 12
monthly_pmnt = Loan × [monthly_rate × (1 + monthly_rate)^months]
÷ [(1 + monthly_rate)^months − 1]
total_paid = monthly_pmnt × months
total_interest = total_paid − LoanWhen the rate is 0%, the payment is simply Loan ÷ months (pure principal repayment).
Monthly payment reference table
For a $10,000 loan at common annual rates and terms:
| Term | 4% rate | 8% rate | 12% rate | 18% rate |
|---|---|---|---|---|
| 6 months | $1,686 | $1,706 | $1,725 | $1,755 |
| 12 months | $851 | $870 | $888 | $917 |
| 24 months | $434 | $452 | $471 | $499 |
| 36 months | $295 | $313 | $332 | $362 |
| 60 months | $184 | $203 | $222 | $254 |
Monthly payment per $10,000 borrowed — scale linearly for other amounts.
French vs. other amortization methods
| Method | Monthly payment | Total interest | Best for |
|---|---|---|---|
| French (this calculator) | Fixed | Medium | Most loans — predictable cash flow |
| German | Decreasing | Lower | Early payoff preference |
| American (bullet) | Interest only + lump sum | Highest | Short-term bridge loans |
How to minimize total interest paid
Frequently asked questions
What is the French amortization method?
French amortization means your monthly payment stays the same throughout the loan. Early payments are mostly interest; later payments are mostly principal. The total amount owed decreases with every payment. It's the standard method used by banks, brokers, and mortgage lenders worldwide.
What's the difference between nominal annual rate and APR?
The nominal annual rate is the base interest rate divided by 12 for monthly compounding. APR (Annual Percentage Rate) adds loan origination fees, insurance, and other charges — making it a more complete cost measure. This calculator uses the nominal rate; ask your lender for the APR to compare total costs across offers.
How much interest do I pay on a $10,000 loan over 3 years?
At 8% annual rate: $10,000 × 36 months at 8% = $313/month, total $11,268, interest = $1,268. At 12%: $332/month, total $11,952, interest = $1,952. At 18%: $362/month, total $13,032, interest = $3,032. Higher rates sharply increase total cost over multi-year terms.
Does a longer term always save money monthly?
Yes on the monthly payment, no on total cost. Extending from 24 to 36 months on a $10,000 / 8% loan drops the monthly payment from $452 to $313 but raises total interest from $835 to $1,268. Choose based on your monthly cash flow vs. total cost trade-off.
How does this apply to broker or investment financing?
Brokers (including Argentine ALyCs) may offer credit lines backed by your portfolio assets. The monthly repayment uses exactly this formula. The interest rate depends on the collateral quality and loan term — use this calculator to verify the monthly installment quoted by your broker.
What if the rate is 0%?
When the annual rate is 0%, the formula simplifies to monthly payment = loan ÷ months. This applies to interest-free installment plans (e.g., buy-now-pay-later schemes or personal loans between individuals).
Can I use this for mortgages?
Yes. Enter the mortgage amount, term in months (e.g., 30 years = 360 months), and the nominal annual rate. The formula is identical. Note that mortgage APR usually includes insurance and origination fees not captured in the nominal rate.
How do I compare two loan offers?
Enter the same amount and term for both offers, changing only the rate. The difference in monthly payment multiplied by the term gives the extra interest cost. Additionally, ask each lender for the APR to capture any fees built into the loan structure.