Adjust any loan amount, rate, and term to instantly see how monthly compounding snowballs your debt. Then understand why Islamic finance calls this riba — and what the halal alternative actually costs.
A = P(1+r/n)^nt
Formula
~$488K interest
$350K at 7% over 30 yrs
Monthly (n=12)
Compounding frequency
Drag the slider to your loan balance — mortgage, car loan, student loan, or any compounding debt. Range: $10K to $2M.
Enter the annual rate your lender quoted. The calculator divides by 12 for monthly compounding automatically.
Choose repayment years. 30 for mortgages, 5–7 for cars, 10–25 for student loans. Watch the curve steepen.
The chart shows the compounding curve. The stats bar shows monthly payment, total paid, and total interest — your full riba burden.
A = P(1 + r/n)nt
Total Amount = Principal × (1 + Rate ÷ Periods)^(Periods × Years)
A
Total Amount
Full repayment — principal plus all compounded interest.
P
Principal
Original loan amount borrowed.
r
Annual Rate
Interest rate as decimal. 7% = 0.07.
n
Periods/Year
12 for monthly compounding. 365 for daily.
t
Time (years)
Total loan term in years.
You pay back 2.4× the original loan. For every $1 borrowed, $1.40 goes to the lender in interest. And in the first year, roughly 80% of every payment is interest — you barely touch the principal.
With a conventional amortized mortgage, each monthly payment is the same dollar amount — but the split between interest and principal changes dramatically over time. In the early years, interest dominates. This is not an accident: the lender collects the most profitable portion of the loan first, ensuring their return even if the borrower sells or refinances early.
| Year | Interest paid | Principal paid | Balance remaining |
|---|---|---|---|
| Year 1 | $24,421 | $3,524 | $346,476 |
| Year 5 | $23,406 | $4,539 | $328,139 |
| Year 10 | $21,851 | $6,094 | $301,706 |
| Year 15 | $19,813 | $8,132 | $268,155 |
| Year 20 | $17,138 | $10,807 | $225,163 |
| Year 25 | $13,626 | $14,319 | $169,614 |
| Year 30 | $8,971 | $18,974 | $0 |
Based on $350,000 at 7% over 30 years. Annual figures approximate.
~80%
of your Year 1 payment is interest
In month 1, only $496 of your $2,329 payment reduces what you owe.
Year 19
is when interest = principal
You don't pay more principal than interest until nearly two-thirds through a 30-year loan.
$488K
total interest on a $350K loan
You pay the lender $1.40 for every $1 borrowed — in addition to returning the full principal.
The Quran explicitly addresses compounding: "O you who believe, do not consume riba, doubled and multiplied" (3:130). Classical scholars interpreted "doubled and multiplied" as a direct description of what happens when unpaid interest is added to the principal and charged interest again — the precise mechanism of compound interest.
Contemporary Islamic economists extend this analysis: compound interest creates a mathematically guaranteed transfer of wealth from borrowers to lenders regardless of real economic conditions. In a recession where incomes fall, the debt still compounds. In a business failure, the interest still accrues. The lender's return is guaranteed; the borrower's burden is guaranteed. Islamic finance considers this structurally unjust — and the exponential curve on this calculator makes that injustice visible.
Each period, interest is added to the balance — then charged interest again next period. The debt grows on itself. The Quran explicitly calls this 'doubled and multiplied' (3:130).
The lender's return is mathematically locked in from day one. Whether your business succeeds or fails, the compound curve doesn't care. Islamic finance requires shared risk.
Amortization ensures the lender collects most interest in the early years. If you sell or refinance, the lender has already extracted maximum profit. It is not a neutral structure.
The bank and buyer co-own the property. Each month, the buyer pays rent on the bank's equity share plus a buy-out installment. As the bank's share decreases, so does the rent. No compound interest — the bank earns rental income on a real asset it actually owns. Available from Guidance Residential, UIF Corporation, Devon Bank, and others across the US.
The bank buys the asset outright and sells it to the buyer at a fixed, disclosed markup payable in installments. The total cost is agreed at contract signing and cannot increase — no compounding, no late-interest penalties. Widely used for auto financing and business equipment in the US.
The bank purchases the asset and leases it to the buyer. Monthly payments are rent, not interest. Ownership transfers at the end of the lease. Because the bank holds title and bears ownership risk throughout, the structure is Sharia-compliant — unlike a conventional lease where interest is embedded in the payments.
Interest calculated on the principal plus all previously accumulated interest. Formula: A = P(1 + r/n)^nt. Creates exponential debt growth. The standard model for US mortgages, credit cards, and student loans.
The repayment structure where each payment is fixed but the split between interest and principal changes over time. In early years, most of each payment is interest. The lender collects maximum return in the first half of the loan term.
Any predetermined guaranteed return on a loan — prohibited in the Quran (2:275–279; 3:130). Compound interest is considered the most harmful form: 'doubled and multiplied' — which is exactly what compounding does mathematically.
The original borrowed amount. With compound interest, you pay interest on this figure — plus interest on the interest already charged. With Musharakah, only rent on the bank's actual equity share is charged.
Diminishing co-ownership. Bank and buyer jointly own the property. Buyer gradually buys out the bank's share while paying rent on the remaining portion. Rent decreases as ownership transfers — no compounding.
How often interest is calculated and added to the balance per year. Monthly (n=12) is standard for mortgages and student loans. Daily (n=365) is used for credit cards, making them even more expensive.
Compound interest is calculated using A = P(1 + r/n)^(nt), where P is the principal, r is the annual interest rate as a decimal, n is the number of compounding periods per year (12 for monthly), and t is the term in years. For example, a $350,000 mortgage at 7% compounded monthly over 30 years results in a total repayment of approximately $838,000 — more than $488,000 in interest alone.
Simple interest is calculated only on the original principal using I = P × r × t — it grows in a straight line. Compound interest is calculated on the principal plus all previously accumulated interest, causing exponential growth. A $350,000 loan at 7% for 30 years costs $735,000 in simple interest but approximately $488,000 in compound interest (amortized monthly). Although the compound figure appears lower, monthly compounding means you're paying interest on interest every single month throughout the term.
In the early years of a compounded loan, almost your entire monthly payment goes to interest — not principal. On a 30-year mortgage at 7%, roughly 80% of your first payment is interest. This means you build equity extremely slowly at first and owe nearly the full principal for many years. Simple interest, by contrast, applies the same charge each period with no snowballing. Islamic finance avoids both by structuring payments as rent on co-owned equity (Musharakah) rather than interest on debt.
Yes. The majority scholarly position holds that all forms of interest — simple or compound — constitute riba and are prohibited (Quran 2:275–279). Compound interest is considered especially harmful because it charges 'interest on interest,' which classical scholars identified as riba al-fadl compounded by riba al-nasi'ah. Some scholars note that the Quran's specific warning — 'do not consume riba doubled and multiplied' (3:130) — directly describes the compounding mechanism.
A conventional mortgage uses monthly amortization: the lender calculates interest on the outstanding balance each month, then applies your payment — first to interest, then to principal. Because the balance reduces slowly in the early years, the interest component dominates. By the midpoint of a 30-year mortgage, a borrower has typically repaid only about 25–30% of the original principal despite making half the total payments. This structure is what Islamic finance replaces with Musharakah, where equity builds proportionally from the start.
The primary halal alternative in the US is Musharakah (diminishing partnership), offered by providers like Guidance Residential, UIF Corporation, and Devon Bank. The bank and buyer co-own the home. The buyer pays monthly rent on the bank's share plus a buy-out installment. As ownership shifts, rent decreases. No interest compounds — the bank earns rental income on a real asset it actually owns. Murabaha (cost-plus sale) and Ijara (lease-to-own) are also available for shorter-term financing.
Yes. Enter the balance as P, the APR as r, and the repayment period as t. Note that credit cards typically compound daily (n=365) rather than monthly (n=12), so this calculator will slightly understate their true cost. For student loans and car loans, monthly compounding is standard and results will be accurate. The monthly payment shown uses the standard amortization formula and reflects what you'd pay to fully retire the debt in t years.
Related Tool
See how simple interest (A = P(1+rt)) compares to compound — and understand the difference in riba burden between a linear and exponential loan.
Open calculatorRelated Tool
Full side-by-side comparison of a conventional amortized mortgage vs Islamic Musharakah co-ownership. Year-by-year equity charts included.
Open calculatorRelated Guide
The Quranic basis for the riba prohibition, classical scholarly analysis, and what it means for American Muslims navigating mortgages and loans today.
Read the guideRelated Guide
Musharakah, Ijara, and Murabaha compared. Which US providers offer them, what states they serve, and how to apply.
Read the guideThis calculator uses the compound interest formula A = P(1 + r/n)^nt with monthly compounding (n=12). Monthly payment uses the standard amortization formula. Credit cards typically compound daily and will cost more than shown. Results are estimates for educational purposes only — not financial or legal advice. Islamic finance rulings vary by scholar and madhab. Consult a qualified Islamic scholar for guidance specific to your situation.