# Interest Rate – David Cantrell’s Solution Method

Use David Cantrell’s solution method and calculate interest rate using this free calculator.

## David Cantrell’s Solution Method

Initial Amount (A) :

Payment Amount (P) :

Number of years (n) :

Interest Rate (i) (%) ≈

**Formula:**

i ≈ [ ( 1 + ( P/A ) )

^{ 1/q }- 1 ]

^{ q }- 1

Where,

q = log[ 1 + (1/N) ] / log2

N = n * 12

P = Payment Amount

A = Initial Amount

N = Number of Payments