# How to make a ROM (Rough Order of Magnitude) Estimation? Without a Crystal Ball?

Time to Read 6 min

This is the more challenging case than the project estimation. How to make an estimate when the requirements and even the architecture of a product are not yet clear? How to make an effort estimate when only a first idea is sketched on an A4 sheet?

How can you get the maximum out of the available information? The maximum here means: In what range is the expected effort?

## Tea Leaves Reading for a Coffee Machine Controller

Such an example was the development of a control system for a coffee machine in the initial phase. The project ended up covering several person-years of work. The initial estimate was based on the information available at the time: a specification of twelve pages including cover page and table of contents, and a rough menu tree for operation...

How can an estimate be generated for a project at this early stage that is not just pure tea leaves reading?

### What can You Expect?

**System Design**: Should you really do it already with the data available?**Functional Breakdown Structure**: How to avoid the system design effort**Estimation of the Effort as a Team**: These are the few estimation steps**A Little Probability Calculation is Required**: The confidence interval

And on separate pages:

**Estimation: What Should be Considered in Practice?****Models: How to Deal with Fuzziness? Distributions!**

We have been working with this estimation method for many years and have created a software tool for it, which we offer as freeware if there is enough interest, please comment below if you are interested.