This folder contains content which, whilst correct at the time posted, may have been superseded by newer tariffs or changes to terms and conditions.

The information has been archived to enable customers on legacy tariffs to refer back to it, but note that it will not be updated, so may not be a full representation of the current status of the tariffs referred to.

Capacity Calculations

There have been previous attempts to cost 1GB of bandwidth, and we realise this checker differs from other attempts at calculation.

The reasons why our calculation may differ from others is that

1) We have based the costs on the price of a BT Central 622 Mbit/s L2TP Passthrough which is £1,758,693.00 pa
(which is more expensive than 4 x 155 Mbps £371,535.00 = 1,486,140) = £272,553 dearer.
Most medium and large ISP's will use the 622 product. - Plusnet certainly do hence why we have used the 622 as a base cost.

2) I have included VAT in my costings.
The home user pays VAT on the product he purchases from the ISP therefore it makes it easier for someone to understand the end cost they have to pay.
If you are calculating the end cost to the consumer then you cant mix ex-VAT and VAT inc figures. You stick to one set or the other.
At the end of the day Plusnet will still have to pay/collect the VAT portion to HMC&E at some point.



Calculating the cost per GB is no mean feat and is subject to many variables therefore we have used the following method which gives an indication of the minimum cost to an ISP if their pipes were maxed out 24/7. Under-utilised pipes will cost much more than this.

For the calculation we use the following formula:-

var bt622cost = 1758693/12; // £ per month
var totalthroughputpm = 622 * 1.5 / 8 * 60 * 60 * 24 * 30 / 1000;

622 * 1.5 gives us the value for up and downstream which is the total throughput on the pipe
dividing by 8 gets the MBytes rather than Megabits
* 60 gets the mins
* 60 gets the hours
* 24 gets the days
* 30 gets the month
/ 1000 gives us the GB figure. (plusnet and BT Radius monitoring use 1000 rather than 1024).

var costpergb = bt622cost / totalthroughputpm;

as an additional variable we also show the downstream only figure

var gbdownstream[1] = gb[1] * 2/3;
which is the same as
622 / 8 * 60 * 60 * 24 * 30 / 1000;

Theres a very good article written by Mr Saffron from adsl guide here which explains cost per GB in more detail

The reason why his calculation comes out at 52p is simply because he has used the exVAT cost of a 155Mb pipe which is cheaper.
Aside from that all the other variables are the same.

Article last edited on Saturday, 13-Mar-2010 01:06 AM