Flat Interest Loan Effective Cost Calculator
Compare add-on flat interest with the effective annual borrowing cost implied by monthly repayments and a deducted fee.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Calculate flat interest on the original stated principal for the entire term. Solve monthly IRR using net received proceeds against equal end-month payments.
Flat interest=P×flat rate×months/12; effective annual cost=(1+monthly IRR)^12−1
Worked example
Principal 1200, flat rate zero, 12 monthly payments and no fee gives payment 100 and effective annual cost 0%. Positive flat interest usually implies a higher effective annual rate than the quoted flat rate.
Assumptions and input details
Fee is withheld at origination, not financed or charged again in monthly payments. Net proceeds must be positive. Equal monthly timing, no grace period, balloon, irregular dates, insurance or other charges. The calculated effective annual cash-flow rate is not a jurisdiction-specific statutory APR. No live market data or national tax rules are inferred. Enter consistent amounts in one currency unless explicitly stated otherwise.
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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