How long should a customer interview be?

About 20 minutes is enough for a first round. Ask fewer questions and follow up on specific stories.

Should I offer an incentive?

A small thank-you is fine, but people who only come for a reward give weaker evidence. Many people help simply because you asked about their problem.

Where do I find people to interview?

Start with communities where the segment already talks, your own network and introductions from each interviewee. The linked guide covers specific channels.

Free tool

Free customer interview planner

Plan your first ten customer interviews in one minute: how many people to message, a week-by-week schedule, a non-salesy outreach message and a 20-minute interview script focused on past behaviour. Free, no account needed.

Who you'll interviewThe problemInterviews per week

Your plan

10 interviews over 4 weeks. Send about 40 messages — roughly 1 in 4 people say yes.

Week 1: send 12 messages, hold 3 interviews
Week 2: send 12 messages, hold 3 interviews
Week 3: send 12 messages, hold 3 interviews
Week 4: send 4 messages, hold 1 interview

Outreach message

Hi [name], I'm researching how people like you handle this part of your work. I'm not selling anything — could I ask you about the last time it came up? 20 minutes, any day this week. Happy to share what I learn.

20-minute interview script

Warm-up and context (3 min)
Walk me through your role and where this part of your work fits in a normal week.
The last time (7 min)
Tell me about the last time this part of your work happened. What triggered it and what did you do next?
Workarounds and cost (5 min)
What have you tried to fix it? What does it cost you in time or money today?
Decision and budget (3 min)
Who else is involved when you pay for a fix? Have you bought anything for this before?
Wrap-up (2 min)
What should I have asked but didn't? Who else should I talk to?

Track every interview against your riskiest assumptions in a free Vouch workspace.

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Your next research step

After each conversation, paste your notes into the transcript analyser to separate evidence from compliments.

Continue the research loop Customer and offer research

Why the plan starts with ten interviews

Ten conversations within one narrow segment is usually enough to hear the same stories repeat, without spending months. If you change the segment, start a new round of ten.

Cold outreach often gets a yes from roughly one in four people, so the planner budgets about four messages per interview. Warm introductions convert better; use them first.

How to use the script

The script spends most of the time on the last time the problem happened, what people tried and what it costs them. Never pitch the idea during the interview; pitching turns evidence into politeness.

Record (with permission) or take notes, then paste them into the free transcript analyser to separate real evidence from compliments.

Who this tool is for

First-time founders who don't know how to start customer discovery
PMs planning a round of user research for a new feature
Builders who want an outreach message that doesn't sound like a pitch

Questions founders ask

How long should a customer interview be?: About 20 minutes is enough for a first round. Ask fewer questions and follow up on specific stories.
Should I offer an incentive?: A small thank-you is fine, but people who only come for a reward give weaker evidence. Many people help simply because you asked about their problem.
Where do I find people to interview?: Start with communities where the segment already talks, your own network and introductions from each interviewee. The linked guide covers specific channels.

Facts you can quote

Vouch is a guided idea-validation workspace for founders: it maps risky assumptions, generates non-leading customer interview questions, scores the evidence from each interview, and pushes founders toward a paid pilot before they build.
Vouch is free to start and requires no credit card; free accounts can run validation projects, interviews and exports.
Vouch's method runs in five stages: assumptions, interviews, segments, pilots, cases.

Source: Vouch (vouch.specky.space) — idea validation workspace for founders. Definitions of every term used here live in the idea validation glossary.

Deeper read: How do you find people to interview for a startup idea?

More free tools: Customer interview question generator · Ideal customer profile (ICP) builder · Startup idea validation checklist · Product-market fit survey · Interview transcript analyser

Vouch keeps the whole loop in one place — assumptions, interview transcripts, evidence scoring, and paid-pilot templates. Start free