Loan Comparison Calculator
Put two loan offers side by side and see which one actually costs less once the monthly payment and total interest are both on the table.
Formula and sources updated · Data sources · 1View algorithm, constants and default inputs (JSON)
Total interest
About this calculator
A shorter term usually means a higher monthly payment but far less interest. A lower rate on a longer term can look cheaper month to month while costing more overall. This calculator shows both numbers so the trade-off is visible instead of implied.
Worked example
calculated with the default values below
Amount borrowed 200,000 $ · Loan A interest rate 5.5 % · Loan A term 30 years · Loan B interest rate 4.8 % · Loan B term 15 years Monthly payment · A / B 1135.578002694001 / 1560.8288702026657 · Loan A monthly payment 1,135.58 $ · Loan B monthly payment 1,560.83 $ · Loan A total paid 408,808 $ · Loan B total paid 280,949 $ · Loan A total interest 208,808 $ · Loan B total interest 80,949 $ · Total interest difference 127,859 $ · Loan A term 30 years · Loan B term 15 years
Method and assumptions
Formula basis and scope
Fixed monthly payment = P × i / (1 - (1 + i)^(-n)); i is annual percent / 1200. At zero interest, payment = P / n.
Fixed nominal rate and monthly payments; fees, insurance, taxes and lender-specific daily accrual are excluded. Each term is rounded to a whole number of months; lower monthly payment does not mean lower total interest.
Data sources
Disclaimer
These calculators give estimates for general information only. They are not financial, tax or investment advice and do not take your personal circumstances into account. Before borrowing, investing or filing, confirm the numbers with a qualified adviser in your jurisdiction.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
M = P × r × (1 + r)^n ÷ ((1 + r)^n − 1); r = rate ÷ 100 ÷ 12; n = round(years × 12); total = M × n; interest = total − P
- P
- loan amount
- rate
- annual interest rate (%)
- years
- term in years
- r
- monthly interest rate
- n
- number of months
- M
- monthly payment
Applied to offers A and B; interestSaving = |interest A − interest B|; if r = 0, M = P ÷ n.
Frequently asked questions
What does the comparison actually include?
It calculates each loan’s monthly payment, total paid and total interest from the same principal and the entered rates and terms. It does not accept APR, origination fees, closing costs, prepayment penalties or rate changes.
Why can a lower rate still have a higher monthly payment?
A shorter term can raise the monthly payment even at a lower rate, while often reducing total interest. The tool compares two fixed-rate amortization scenarios from the entered numbers. It does not model fees or early repayment, so the displayed interest saving is only the absolute difference between modeled interest totals.