How to use
- Select loan or investment mode and enter PV, PMT, and NPER.
- Adjust timing, FV, and periods per year if needed.
- Review periodic rate, APR, EAR, and generated Excel RATE formula.
Inputs
Result
Notes
- The solver uses bracket search plus iterative root-finding.
- Sign convention is adjusted automatically by selected mode.
- Real contracts may include fees, taxes, or step-up payments not modeled here.
FAQ
What is the difference between APR and EAR?
APR is nominal annualized rate, while EAR includes compounding effect across periods.
Why does the solver fail for some inputs?
Some cash-flow combinations have no real solution. Check payment amount, periods, and sign direction.
Does it match Excel RATE?
Yes when sign convention, payment timing, and FV assumptions are aligned.
How are PMT and FV treated in investment mode?
In investment mode, PV and PMT are treated as outflows and FV as an inflow through internal sign normalization. In most cases, enter positive amounts. Special cases such as recurring dividend receipts are outside this simplified model.
What changes with beginning-of-period payments?
Beginning payments happen earlier, so the required rate is usually lower under the same conditions.