How does one work out when it's appropriate to move to the cloud. At what point do you decide that it's cost effective move?

That's going to be one of the key questions faced by any organisation looking to do this. Of course, it's not the only question - security is always going to be an issue, compliance will come into consideration and there are going to be HR allocation to be taken into account - but cost effectiveness is going to be a key element.

So, it's no surprise that there's been a sudden flurry in ROI calculators, all designed to aid the wavering executives help decide whether a move to the cloud is practical or not, or more to the point, whether it's cost effective or not.

There are two sorts of calculators: those provided by software management companies where the calculator is seen as adjunct to their more comprehensive offerings, and calculators provided by cloud vendors - which do rather have an interest in skewing the results. How likely are we to see the calculator from the likes of Amazon or Microsoft telling a prospective punter that he'd be better off sticking with on premise?

I started thinking about the question because I've just received the second press release this week offering a cloud ROI calculator, this very latest from Astadia.  I suspect that this is going to be the tip of the iceberg and am about to be inundated with them.

Let's look at the detail of the Astadia one. It looks comprehensive enough with seven different variables for IT hardware - the likes of network and storage costs - allied with IT services such as disaster recovery and security.

But there are caveats. Firstly, according to the Astadia release, the ROI calculator is optimised for, so if you're going to be using another cloud platform, the calculation may be a bit wayward.

There's also no weighting: there are going to be some organisations that place a higher premium on security than others. There will be some with particularly intensive demands on storage - that emphasis won't necessarily be reflected in factors such as increased spending on those areas. Nor does it take other factors into account: there could well be personnel issues to deal with.

Having said that, the Astadia offering is a good deal more comprehensive than others I have seen and does attempt to come to terms with the multi-faceted aspects of IT. But all these calculators will come up against a single flaw - it's almost impossible to calculate all the financial ramifications of moving to cloud.

To be fair to Astadia (and all the other producers of these calculation tools), there's little pretence that this is a definitive answer to the problem of assessing costs when moving to cloud. The calculating tools are a helpful resource but not a long term solution when it comes to looking at how cloud computing can be implemented across an enterprise. Guess there's no real substitute for trusty spreadsheets and the good old-fashioned finger in the air to see which way the wind is blowing.

Follow Maxwell on Twitter