What could better measure your release’s agility than a wiggle room calculator? It’s a companion to the release calculator described in an earlier post.
The release calculator’s job was to work out how many iterations you need to complete your critical functionality with 95% certainty. The wiggle room calculator assumes instead that you’ve roughly sized your release already and tells you how much of your remaining iterations can be committed to critical functionality and (conversely) how much you should keep up your sleeve. This contingency can be kept for the unforeseen and – fingers crossed – used later for the nice-to-have stuff.
The contingency calculation looks a little more involved this time. All it is though is a rearrangement of the original calculations having eliminated the “ri” variable.
Try out the wiggle room calculator now!
P.S. Many thanks to Mike Cohn for his feedback on the original calculator. I’ve made some changes already as a result; longer term I’ll allow for the entry of historical velocities from multiple iterations so that average velocity and variation can be calculated for you.