老问题：关于每周还款，每月还款，每Fornight还款

helnandez

用NAB和HSBC的loan calculator 算了两遍，答案和实际情况不一样，实际情况的月结是一样的但是周和fornight都不一样实际情况是如果我想要每周还款，但是他的每周还款金额是
月还款金额除以4
按还款35万，30年计算，利息是6.79%无offset，假设利率不变，这样利息到底省了多少呢？总共需要还多少钱呢？我是指FV， FV和以前按月还的FV也不一样了吧，因为天数少了
求解，那这样贴现息按照怎么算呢？
6.79/52也不对了，应该是6.79/48才对？

wcx0314

on a daily base

wcx0314

一个周的interest等于  35万乘以利率  除以365   乘以 7
对否

in2theshine

Weekly repayment is monthly/4, but the total interest would be dramatically reduced since bank caculates the interest on daily base, so if you've paid the first week, the interest wouldn't be charged over that week, for a long time you could save a lot.
Not every bank allows weekly repayment though.

shayy

原帖由 in2theshine 于 2011-10-6 16:43 发表
Weekly repayment is monthly/4, but the total interest would be dramatically reduced since bank caculates the interest on daily base, so if you've paid the first week, the interest wouldn't be charged  ...
So if the repayment is made from an offset account, would there still be any difference?

frankielynna

很难计算，因为你不知道每次还钱，本金利息的比例是多少。干啥费这个脑子，搞个offset, 有钱就放里面就好了。

helnandez

这里不讨论Offset，因为offset就没影响了，我想知道的是用多少年能还完原来30年的贷款？怎么算？
[ 本帖最后由 helnandez 于 2011-10-6 13:55 编辑 ]

helnandez

原帖由 frankielynna 于 6-10-2011 13:47 发表
很难计算，因为你不知道每次还钱，本金利息的比例是多少。干啥费这个脑子，搞个offset, 有钱就放里面就好了。 不对，你知道年金，这里可以用 每月还款/4
贴现息是6.79%/48
但是我只知道PV 35万
FV不知道，R其实也不知道……
两个未知数，这公式咋算呢？

in2theshine

原帖由 shayy 于 2011-10-6 16:45 发表
So if the repayment is made from an offset account, would there still be any difference?
The way is the same, just the interest will be lower for each repayment due to the offset.

in2theshine

原帖由 helnandez 于 2011-10-6 16:47 发表
这里不讨论Offset，因为offset就没影响了，我想知道的是用多少年能还完原来30年的贷款？怎么算？
It's very hard for us to simulate what exactly the length, but roughly it is this way:
1. Monthly repayment interest
Bank caculates interest daily so you pay: 35wx6.79%/365= A each day, but since you wouldn't pay it until end of month, A is on top of 35w, the 2nd day: (35w+A)X6.79%/364=B, and so on, the 8th day: (35w+A+B+C+D+E+F+G)X6.79%/348=H...on the 31th day the monthly repayment is the sum of A+B+C..+H+...
2. Weekly repayment interest
The first 7 days is the same, but the 8th day, since you've paid the first 7 days, it would be (35w-A-B-C-D-E-F-G)X6.79%/348... apparently after 4 weeks, the ammount is less than Monthly repayment