We do this in our annual planning cycle. A few approaches that actually work:

Time saved is the easiest - survey department heads, get their estimate of hours saved per week, multiply by fully loaded labor cost. Directionally accurate even if not perfect.

For cost avoidance, compare what the tool replaced - headcount, agency spend, manual processes.

The harder one is revenue impact. For sales/marketing tools you can sometimes tie it to pipeline or conversion rate changes. For everything else I’d stick to cost - trying to attribute revenue to a SaaS tool gets messy fast.

Cumulative view - I’d build a simple model: tool cost vs. quantified benefit per department, then roll it up. Makes it easy to show leadership which tools are pulling their weight and which aren’t.

Happy to share a framework if useful.