抵押计算器数学

Question

这个程序运行得很好，但它返回的每月付款是完全不可用的。如果本金为400000美元，利率为11%，付款期为10年，则每月返回44000.16美元。我在谷歌上搜索了方程（算法？）我不知道我哪里出错了。在

import locale
locale.setlocale(locale.LC_ALL, '')

def mortgage(principal, interest, n):
    payment = principal*((interest*(1+interest)**n) / ((1+interest)**n-1))
    return payment

principal = float(input("What is the amount of the loan you are taking out? $"))
interest = float(input("What is the interest rate? (%) ")) / 100
n = float(input("How many years? ")) * 12
print
print "Your monthly payment would be", locale.currency(mortgage(principal, interest, n))

Answer 1

问题在于你使用的利率。你要求的是年利率，而不是月利率。在

来自https://en.wikipedia.org/wiki/Mortgage_calculator#Monthly_payment_formula：

r - the monthly interest rate, expressed as a decimal, not a percentage. Since the quoted yearly percentage rate is not a compounded rate, the monthly percentage rate is simply the yearly percentage rate divided by 12; dividing the monthly percentage rate by 100 gives r, the monthly rate expressed as a decimal.

我刚在我的电脑上试过，把利率除以12，计算出5510美元/月，这与其他抵押贷款计算器是一致的。在