Although there are many available mortgage calculators out there, the principle of a simple mortgage calculator is really simple, which is based on the following math formula.

where, the *c* is the monthly repayment, *r* is the monthly interests (which is the one-twelveth of the yearly interests). *P* is the total money borrowed. *N* is the total number of re-payments (e.g. the number of months).

### Simple Mortgage Calculator Implemented in MySQL

For example, I borrowed 170K from the HSBC Bank, the interests rate (yearly) is 2.49%, and I need to repay the principle+interests in 25 years. The amount of repayment each month (suppose it is fixed-rate) can be computed via the following command in MySQL console:

mysql> select 0.0249/12*170000*power(1+0.0249/12,25*12)/(power(1+0.0249/12,25*12)-1); +------------------------------------------------------------------------+ | 0.0249/12*170000*power(1+0.0249/12,25*12)/(power(1+0.0249/12,25*12)-1) | +------------------------------------------------------------------------+ | 761.792586559163 | +------------------------------------------------------------------------+ 1 row in set (0.00 sec)

### Simple Mortgage Calculator Implemented in C/C++

With the *pow* function from *math.h*, the payment function is defined as follows:

1 2 3 4 5 6 7 8 9 |
#include <math.h> // r - monthly interest rate // p - principle // n - number of repayments double payment(r, p, n) { var x = pow(1 + r, n); return r * p * x / (x - 1); } |

### Online Simple Mortgage Calculator Implemented in Javascript

Similarly, the function defined in Javascript is defined as:

1 2 3 4 5 6 7 |
// r - monthly interest rate // p - principle // n - number of repayments function payment(r, p, n) { var x = Math.pow(1 + r, n); return r * p * x / (x - 1); } |

Fill in the values of *r*, *P* and *N* and the the following online mortgage calculator (open in new window) will compute the monthly repayment and interests (not available if you are viewing in Accelerated Mobile Page version):

The alternative version of this mortgage calculator can be found here.