Kamatni račun

Interest calculation,

Keywords: interest calculation, simple Interest, compound Interest, investment, annuity, interest rates, principal

Simple Interest

Interest i for the principal P with an interest rates of  r %:

i=P·r100

Interest coefficient q in case the interest rate is r %:

q=100+r100=1+r100

Increased value of principal P increased with interest at the interest rate of r %:

P+i=P·q

Compound Interest

Value of principal Pn  after n years with an interest rate of r % in case of starting principal P0:

Pn=P0·1+r100n

Value of principal Pn  after n years with an amortization rate of r % in case of starting principal P0:

Pn=P0·1-r100n

Discount value of principal Pn with an interest rate of r %:

P0=Pn·100100+rn

Increase of annuities a after n years:

Sn=100·apqn-1

Investment

Availabel amount after n years in case of annuity investment a (amount, invested each year),
if the payment is at the beginning of each year:

Sn=aq·qn-1q-1

Availabel amount after n years in case of  annuity investment a (amount, invested each year),
if the payment is at the end of  each year:

Sn=Sn*=a·qn-1q-1

Installment (annuity) of the loan P on an annual basis, if the repayment rate is due at the end of the year:

A=P100·qn·rqn-1