Simple (Flat Rate) Interest Calculator: Calculate the Annual Simple (Flat) Interest Rate of the Invested Amount of Money (Principal, Initial Starting Amount Lent, Deposited or Borrowed), of 100 units (Dollar, Euro, Pound, etc.) To Produce a Sum of Money of 200 units, for a period of 2,585 days (85 Months). The transaction fee is 670%

Detailed calculations of the simple (flat) interest rate

Notations and variables used:

Principal (initial amount), P = 100


Amount produced by the interest, I = 200


From date: Feb 28, 2018


To date: Mar 28, 2025


Duration, T = 2,585 days (85 Months)


Transaction fee rate, F% = 670%

Transaction fee amount, F


Number of days in a year, N = 365

Calculate R, the annual simple (flat) interest rate to earn the amount I

The simple (flat rate) interest calculation formula:

I = (P × R × T) ÷ N ⇒


R = (N × I) ÷ (P × T) =


100% × (N × I) ÷ (P × T) =


((100 × N × I) ÷ (P × T))% =


((100 × 365 × 200) ÷ (100 × 2,585))% =


(7,300,000 ÷ 258,500)% ≈



28.239845261122% ≈


28.24%

Calculate E, the amount earned after adding to the principal the amount produced by the simple (flat rate) interest

E = P + I =


100 + 200 =


300


Calculate L, the amount left after deducting the transaction fee

F = F% × E ⇒

L = E - F =


E - F% × E =


(1 - F%) × E =


(1 - 670%) × 300 =


- 570% × 300 =



- 1,710

Calculate Pr, the profit of the investment

Pr = L - P =


- 1,710 - 100 =


- 1,810

Calculator: annual simple interest rate to negociate to earn a certain amount

Annual simple flat interest rate = (Simple flat rate interest × Number of days in a year) ÷ (Principal × Duration in days)

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All the annual simple flat interest rates calculated by users


How to calculate / negociate the simple flat interest rate of a principal - initial starting amount of money lent, deposited or borrowed, in order to collect or pay a certain simple flat rate interest by the duration and any additional transaction fees (withdrawal, payment in advance, etc.).

Annual simple flat rate interest formula:

  • I = S × p% × n

  • I = n years simple interest charged
  • S = initial amount (principal)
  • p% = annual simple flat interest rate (percentage of the principal, charged as interest)
  • n = number of years of the lending or borrowing the money
  • Formula of the simple flat interest rate applied on the principal - initial starting amount of money lent, deposited or borrowed, in order to earn a simple flat annual rate:

  • p% = I ÷ (S × n)

Examples of how to calculate the simple flat interest rate on the principal amount in order to earn a certain simple flat rate interest:

  • 1) What is the simple flat interest rate of the principal S = 20,000 units that has to be lent, deposited or borrowed, for a period of n = 5 years, if the simple flat rate interest collected or paid D = 3,500 units?
    Answer:
    p% = I ÷ (S × n) = 3,500 ÷ (20,000 × 5) = 3,500 ÷ 100,000 = 3.5 ÷ 100 = 3.5%
  • 2) What is the simple flat interest rate of a principal S = 5,000 units, that has to be lent, deposited or borrowed, for a period of n = 3 years, if the simple flat rate interest collected or paid D = 300 units?
    Answer:
    p% = I ÷ (S × n) = 300 ÷ (5,000 × 3) = 300 ÷ 15,000 = 3 ÷ 150 = 1 ÷ 50 = 2 ÷ 100 = 2%

Annual simple flat interest rate formula calculated for a period of n years:

  • Simple flat interest rate, p% = I ÷ (S × n)
  • Interest, I = S × p% × n
  • Principal, S = I ÷ (p% × n)
  • Number of years of the period of the deposit, lending or borrowing, n = I ÷ (S × p%)

Formula of the simple flat interest rate of the principal for an annual simple flat rate interest calculated for a period of m months:

  • Simple flat interest rate, p% = (12 × I) ÷ (S × m)
  • Interest, I = (S × p% × m) ÷ 12
  • Principal, S = (12 × I) ÷ (p% × m)
  • Number of months of the period, m = (12 × I) ÷ (S × p%)

Formula of the simple flat interest rate of a principal for an annual simple flat rate interest calculated for a period of d days:

  • Simple flat interest rate, p% = (365 × I) ÷ (S × d)
  • Interest, I = (S × p% × d) ÷ 365
  • Principal, S = (365 × I) ÷ (p% × d)
  • Number of days of the period, d = (365 × I) ÷ (S × p%)

More examples of how the simple flat interest rate of a principal for a simple flat rate interest formula works:

  • 1) Calculate the simple flat interest rate of the initial amount S = 400 units that would generate a simple flat rate interest I = 6.67 units in m = 5 months.
    Answer:
    p% = (12 × I) ÷ (S × m) = (12 × 6.67) ÷ (400 × 5) = (12 × 6.67) ÷ 2,000 = 80 ÷ 2,000 = 4%
  • 2) Calculate the simple flat interest rate of the initial amount S = 400 units that would generate a simple flat rate interest I = 7.5 units in m = 5 months.
    Answer:
    p% = (12 × I) ÷ (S × m) = (12 × 7.5) ÷ (400 × 5) = 90 ÷ 2,000 = 4.5%.