AltF IdeaLab

Assumption mapping tool

The assumption mapping tool sorts each belief your idea depends on into one of four quadrants and ranks them, riskiest first. You rate importance and evidence from 1 to 5, and important assumptions with little evidence go to Test now. The ratings are your judgement, so the ranking is only as good as your honesty about the evidence.

  • Free, no sign-up
  • Runs in your browser
  • No AI guesswork
  • Export to Markdown

How to use the assumption mapping tool

  1. 1

    List your assumptions

    Write each belief the idea depends on, or start from the four starter assumptions.

  2. 2

    Tag the type

    Mark each one as desirability (do people want it), viability (can it make money) or feasibility (can we build and deliver it).

  3. 3

    Rate importance and evidence

    Score importance and current evidence from 1 to 5 for each assumption.

  4. 4

    Test the top of the list

    Start with the highest-risk items in Test now and plan an experiment for each.

How it works

  • Importance of 4 or 5 counts as important; evidence of 3 or less counts as unproven.
  • Important and unproven is Test now, important and proven is Keep an eye on, unproven but less important is Park for later, and the rest is Low priority.
  • Risk score = importance x (6 - evidence), so the range runs from 1 to 25.
  • Assumptions are listed from highest risk score to lowest.

Worked example: the four starter assumptions

"They will pay a recurring fee rather than keep the current workaround": importance 5, evidence 1, risk 5 x 5 = 25, Test now.

"The target audience feels this problem at least weekly": importance 5, evidence 2, risk 5 x 4 = 20, Test now.

"We can reach the first 50 buyers without paid ads": importance 4, evidence 2, risk 4 x 4 = 16, Test now.

"A first version can be delivered manually in under two weeks": importance 3, evidence 3, risk 3 x 3 = 9, Park for later.

What the assumption mapping tool does not do

  • Importance and evidence are your own ratings; the tool cannot check them.
  • Assumptions you never write down cannot be ranked, so ask a co-founder or mentor to add theirs.
  • Ties in risk score keep the order you entered them in.

Assumption mapping tool FAQ

What is an assumption map?

A grid that plots each assumption by how important it is and how much evidence backs it, so you test the important, unproven ones first.

How is the risk score calculated?

Importance multiplied by (6 minus evidence). An assumption rated importance 5 and evidence 1 scores the maximum of 25.

Where is the cut-off between quadrants?

Importance 4 or above counts as important, and evidence 3 or below counts as unproven.

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