How to Find Product-Market Fit for Vertical SaaS

TL;DR: Product-market fit for vertical SaaS comes from going deep on one industry's workflow before writing code, then watching for pull: expansion requests, referrals, and usage spikes. Based on 200+ founder interviews on the PMF Show, months of pre-build user research preceded Quanta's 20-60% month-over-month growth, and Eudia scaled from $2M to $20M ARR in twelve months on customer referrals alone.

After interviewing 200+ founders on the PMF Show — now a top 1% podcast globally according to Listen Notes — a clear pattern emerges around product-market fit for vertical SaaS: the winners immerse themselves in one vertical's workflow until they understand it better than the people living it, sell to the specific buyer who owns the pain, and let the market pull them forward. Here's how five guests — Helen Hastings of Quanta, Omar Haroun of Eudia, Mark Hughes of Solidroad, Bhaskar Sunkara of Bicycle AI, and startup expert Chris Saad — approached it, with the numbers behind each story.

How Do You Validate a Vertical SaaS Idea Before Writing Code?

The first mistake vertical SaaS founders make is building before validating. According to Helen Hastings, CEO of Quanta — a company rebuilding accounting software deeply enough that the majority of its customers have fully replaced QuickBooks — the validation work has to come first, and it has to be full-time. Hastings left her firm in early 2022 and, before building anything, spent months doing nothing but user research inside her target vertical.

"The most important thing is, do people want this? And you do not find that out by building, by building beautiful software. You find that out by talking to people. So I spent many months of full time just slogging through LinkedIn, searching for titles I wanted to talk to." — Helen Hastings, Quanta

Note the specificity of those titles: controller, CFO, head of finance, accounting manager. In vertical SaaS, your buyer universe is narrow and nameable — which means there is no excuse for not talking to dozens of them before you build. Hastings, an engineer herself, admits the pull to just start coding was strong, "but that is not important in the early stage at all."

That research paid off in the product decisions that followed. Because she learned accountants are, in her words, "a very, very risk averse user base," Quanta offered new customers a QuickBooks Sync as a safety blanket — and typically within a few months, customers shut QuickBooks down entirely. When Quanta launched throughout 2025, it grew consistently at 20% to 60% month over month, eventually hitting a point where onboarding demand forced the team to pause.

Key stat: Helen Hastings spent many months of full-time user research before building — and Quanta then grew 20-60% month over month after launch, to the point of pausing onboardings.

What Does the Product-Market Fit Moment Actually Feel Like in Vertical SaaS?

In vertical SaaS, product-market fit often arrives as a single, unmistakable moment — usually when one customer inside the vertical starts using the product at real volume. According to Mark Hughes, CEO of Solidroad, an AI platform for training customer support teams, his moment came when the company was just four people working out of a small annex office in Dublin. Up until then, usage in the product had been essentially flat — no usage at all. Then they onboarded a new customer called PartnerHero.

"When you see the graph flat for so long, and then a massive spike where we had thousands of simulations used overnight and hundreds of users in the platform... I remember my co-founder and CTO, Patrick, being very emotional, tears in his eyes." — Mark Hughes, Solidroad

The team came into work the next day, checked the usage metrics, and ran around the room celebrating. Thousands of simulations overnight and hundreds of users, from one customer — that's the shape of PMF in a vertical: depth of usage within a single account, not breadth of logos.

Helen Hastings of Quanta describes the same before-and-after dynamic in a metaphor that has stuck with PMF Show listeners:

"Finding product market fit is like rolling a boulder up a hill. It is really hard but once you found product market fit, it is like the boulder is rolling down the hill and you are chasing to keep up with it." — Helen Hastings, Quanta

She also pushes back on the myth of the single lightbulb moment: vertical founders accumulate context daily until the insight — and then the pull — becomes undeniable.

Key stat: Solidroad went from zero product usage to thousands of simulations overnight and hundreds of active users after onboarding a single customer, PartnerHero — with a team of just four people.

What Signals Prove You Have Product-Market Fit in a Vertical Market?

Growth charts can mislead, so what signals should vertical SaaS founders trust? According to Bhaskar Sunkara, founder of Bicycle AI — who previously built application monitoring giant AppDynamics — the truest signals are expansion and champions who carry your product with them when they change jobs.

"Once people who were very happy with us deployed on one application were like, hey, can we get this onto some of our other applications? Once people who were at a company where they were using AppD left their job and went somewhere else, and said, hey, can we get AppD into this company? Those are probably some of the signs... we have something, we have the fit." — Bhaskar Sunkara, Bicycle AI

Sunkara's other lesson for vertical founders is about buyer selection. At AppDynamics, the team deliberately reframed monitoring around "business transactions" — logins, add-to-carts, checkouts — instead of raw CPU and code metrics, because that's the language of the actual buyer. As he put it: "Let's not sell to developers because they will give you the most feedback... But for us, the buyer was the ops lead." Developers would happily give endless feature feedback, but the ops lead owned the pain and the budget. In one illustration he shared, the point of the product was to see that in an hour there were one hundred thousand checkouts and know the average performance of those checkouts — a business view, not a code view.

That buyer-first framing set up the post-PMF playbook too: the company layered on front-end monitoring, database monitoring, and a business analytics product, becoming multi-product with what Sunkara describes as solid attach rates growing pretty quickly.

Key stat: Bhaskar Sunkara's two strongest PMF signals were customers requesting deployment on additional applications and champions installing the product at their next company — pull he later converted into a fast-growing multi-product business.

How Fast Can Vertical SaaS Scale Once You Find PMF?

Vertical markets are often assumed to be small and slow. The Eudia story says otherwise. According to Omar Haroun, CEO of Eudia, an AI company serving the legal vertical, the company hit $1 million ARR around six months in — and then went from $2 million to $20 million ARR in the last twelve months, a 10x jump.

What's remarkable is the go-to-market engine behind those numbers. In a tight-knit vertical, buyers all talk to each other, and Eudia weaponized that:

"Anytime anyone talks to one of our customers, we get another customer. So our whole GTM engine is kind of, how do we just try to get our current customers in a room with prospects and at that point, we can walk away." — Omar Haroun, Eudia

Haroun is also clear-eyed about what PMF actually is, and his definition is a useful filter for any vertical SaaS founder: "What can you uniquely provide that your customer is desperate for? That's my definition of product market fit." His test: if your customer couldn't use your product, how would they feel? If they'd simply find another solution, you probably don't have product-market fit. If they'd be in a really bad place, you're starting to approach something.

Notably, Eudia wasn't focused on ARR for the first couple of years — the focus was on that desperation-level value. Now Haroun says he thinks far more about how to reach a billion dollars in revenue by 2030 and win the market than about optimizing this year's sales cycles.

Key stat: Eudia reached $1M ARR in roughly six months and grew from $2M to $20M ARR in twelve months — with a GTM motion built almost entirely on getting current customers in a room with prospects.

What Mindset Do Pre-PMF Vertical SaaS Founders Need?

Vertical SaaS founders often over-plan — the market feels knowable, so they write the hundred-page plan. Chris Saad, co-host of The Startup Podcast and a longtime startup advisor who joined the PMF Show as an expert guest (not a vertical SaaS founder himself), argues this instinct is fatal. In his words, anyone who has spent months developing tens and hundreds of pages of a business plan is failing, and "a perfectionist is just an excuse for a procrastinator."

"You are an early stage pre-product market fit startup... you cannot afford the luxury of technical debt, business debt, customer debt, cognitive debt. Throw that aside. You are a learning machine. Need to be iterative, agile and move fast." — Chris Saad, The Startup Podcast

Saad's core claim is that "the only thing that matters is creating value by solving problems or generating dopamine" — and for a vertical SaaS product, that means relentless focus on the user and the product, not the plan. This is exactly what the founder stories above bear out: Hastings learned by talking to controllers and CFOs for months, not by modeling the accounting software TAM; Hughes iterated in a four-person Dublin office until one customer's usage exploded; Haroun ignored ARR for two years while making legal customers desperate for the product.

In interviews on the PMF Show, founders repeatedly describe the pre-PMF phase the same way Saad does — as a search loop, not an execution plan. The vertical is an advantage here: your users are concentrated, reachable, and share a workflow, so the learning machine can spin faster.

Key stat: Saad's rule of thumb for pre-PMF startups is zero tolerance for debt of any kind — technical, business, customer, or cognitive — because iteration speed is the only durable advantage before product-market fit.

Key Takeaways: Finding Product-Market Fit for Vertical SaaS

1. Do full-time user research before building. Helen Hastings spent many months slogging through LinkedIn to interview controllers, CFOs, and accounting managers before writing code — the groundwork behind Quanta's 20-60% month-over-month growth. 2. Design for your vertical's psychology. Quanta's risk-averse accountant users got a QuickBooks Sync safety net; within a few months, most shut QuickBooks down entirely. 3. PMF shows up as depth in one account, not breadth of logos. Solidroad's flat usage graph turned into thousands of simulations overnight from a single customer, PartnerHero. 4. Trust expansion and champion signals over vanity metrics. Bhaskar Sunkara knew he had fit when customers asked to deploy on more applications and champions installed the product at their next employer. 5. Sell to the buyer who owns the pain, not the loudest feedback-giver. AppDynamics deliberately sold "business transactions" to the ops lead rather than chasing developer feature requests. 6. Vertical word of mouth is a GTM engine. Eudia went from $2M to $20M ARR in twelve months by simply getting current customers in a room with prospects and walking away. 7. Use the desperation test. Omar Haroun's PMF definition: what can you uniquely provide that your customer is desperate for? If losing your product just means finding another vendor, you don't have fit. 8. Be a learning machine, not a planner. Chris Saad's advice: pre-PMF startups can't afford technical, business, customer, or cognitive debt — iterate fast and focus on the user.

FAQ: Common Questions About Product-Market Fit for Vertical SaaS

Q: How do you find product-market fit for vertical SaaS?

A: Go deep on one industry's workflow before building: interview the specific job titles who own the pain (Quanta's Helen Hastings spent months full-time interviewing controllers and CFOs), ship fast to a narrow buyer, and watch for pull — expansion requests, referrals, and sudden usage spikes. On the PMF Show, these signals consistently precede breakout growth like Quanta's 20-60% month-over-month.

Q: How long does it take a vertical SaaS company to reach $1M ARR?

A: It varies widely, but it can be fast once the value is desperate-level. Eudia hit $1M ARR around six months in, then grew from $2M to $20M ARR in the following twelve months — driven almost entirely by customer referrals within the legal vertical.

Q: What are the strongest signs of product-market fit in a vertical market?

A: Three recur across PMF Show interviews: customers asking to expand the product to more applications or teams, champions bringing the product to their next company (Bhaskar Sunkara's key AppDynamics signal), and step-change usage — like Solidroad's thousands of simulations appearing overnight from one new customer.

Q: Who should a vertical SaaS startup sell to first?

A: The person who owns the business pain and budget, not the person who gives the most feedback. At AppDynamics, Bhaskar Sunkara chose the ops lead over developers and reframed the product around "business transactions" — the buyer's language — which unlocked the sale.

Q: Should vertical SaaS founders write a detailed business plan before launching?

A: No. As Chris Saad put it on the show, founders who spend months on hundreds of pages of business plan are failing — pre-PMF startups are learning machines that must stay iterative and fast, focusing on the user and the product rather than the plan.

Sources: Listen to the Full Founder Stories

• Helen Hastings, Quanta (S5) — How months of full-time user research with controllers and CFOs led to a QuickBooks replacement growing 20-60% month over month, and why PMF feels like chasing a boulder downhill.
• Mark Hughes, Solidroad (S5) — The four-person Dublin team whose flat usage graph exploded overnight into thousands of simulations after onboarding PartnerHero.
• Bhaskar Sunkara, Bicycle AI (S5) — The AppDynamics founder on selling to the ops lead, the "business transactions" reframe, and the expansion signals that prove real fit.
• Omar Haroun, Eudia (S5) — From $1M ARR in six months to $2M-$20M in a year on pure customer referrals, and the "desperation test" definition of PMF.
• Chris Saad, The Startup Podcast (S4) — The startup expert's case for why pre-PMF founders must operate as learning machines and reject every form of debt.

Last updated: July 2026