APR Calculator
finance checks.
Use this tool to calculate APR from flat interest, work backwards from a known APR, or compare annualised interest conventions.
APR Calculator
Calculate APR from flat interest, work backwards from a known APR, or compare annualised interest conventions against the outstanding balance.
- Deposit taken
- £100.00
- Amount borrowed
- £400.00
- Borrowed incl. interest
- £466.60
- Monthly repayment
- £51.84
- Indicative monthly rate
- 3.20%
- Total repayable
- £466.60
Flat interest to APR
- Deposit
- Amount borrowed
- Net advance of credit (A)
- Total flat interest
- Instalment amount (A′k)
- Monthly rate solved numerically
- Effective annual APR
FCA equation balance check
A = Σ A′k ÷ (1 + i)k/12
- Deposit taken
- £100.00
- Amount borrowed
- £400.00
- Net amount advanced
- £400.00
- Monthly repayment
- £51.84
- Total repayable
- £466.60
- Indicative monthly rate
- 3.20%
APR to flat interest
- Deposit
- Amount borrowed
- Net advance of credit (A)
- Monthly rate derived from APR
- Instalment amount (A′k)
- Total interest
- Equivalent flat interest
FCA equation balance check
A = Σ A′k ÷ (1 + i)k/12
- Full-term simple annualisation
- 22.20%
- Average outstanding-balance annualised
- 44.40%
- Average outstanding capital
- £200.00
- Total interest charged
- £66.60
- Equivalent nominal annual reducing rate
- 38.38%
- Equivalent effective APR
- 45.87%
With 16.65% flat interest and 9 instalments, annualising over the 8-month span between instalment 1 and instalment 9 gives 24.975%.
Outstanding capital by instalment
| Instalment | Opening capital | Capital repaid | Closing capital | Average capital |
|---|
Important: these annualised comparison rates are not substitutes for FCA APR. The APR shown above is separately derived from the actual cash flows using the present-value method.
These calculations reproduce the logic used by the supplied spreadsheet. Results are indicative and should be independently checked before being used in regulated customer documentation.