Dec 15, 2023 · 23m · y-combinator
B2B Startup Metrics | Startup School · Y Combinator
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gold bands on the timeline = statements, start to end. Hover to read, click to jump. CC turns on captions
In this Y Combinator Startup School presentation, Group Partner Tom Blomfield outlines essential quantitative metrics for early-stage B2B startups, explaining how to set up tracking before launch, measure true financial health, calculate customer retention, and balance quantitative dashboards with qualitative customer feedback.
How this conversation actually went
Every chapter scored 0–10 on four independent dynamics. Hover any point for the reasoning behind the score. How this is scored →
The partners as informed peer 0.0 Guest teaching 0.0 Guest disagreement 0.0 The partners pushing back 0.0
speaking balance: gold is the partners, purple is the guest (3 minute bins)
Sharpest disagreement ▶ 6:05 Calling out vanity metrics and self-deception
In a lecture setting without interpersonal conflict, Tom's sharpest critique is aimed at founders who use GMV rebates to deceive themselves about revenue growth.
Hardest push from the partners ▶ 1:15 Rejecting post-launch metric implementationTom forcefully pushes back against standard founder practice of launching blind on Hacker News before putting basic instrumentation in place.
Biggest teaching moment ▶ 13:40 Masterclass on Net Dollar Retention targetsTom delivers a definitive masterclass on why early B2B startups should demand >125% NDR due to pricing power, feature expansion, and sales maturity.
The partners hold their own ▶ 19:10 Monzo unit economics turnaround evidenceTom demonstrates deep operational expertise by sharing how Monzo systematically turned -£40 per customer unit economics into +£40 positive contribution.
the scores for every segment, with the reasoning behind each
| Chapter | Topic | The partners as informed peer | Guest teaching | Guest disagreement | The partners pushing back | Why |
|---|---|---|---|---|---|---|
| Building Basic Metrics Before Product Launch | 0 | 0 | 0 | 0 | This is a solo educational presentation by Tom Blomfield. With no host dialogue or counterparty present, all interaction scores are baseline zero. | |
| Essential Guidelines for Pre-Launch Metric Setup | 0 | 0 | 0 | 0 | Tom outlines practical operational advice on picking 4-5 core metrics and keeping metric definitions consistent across internal teams in a monologue format. | |
| Revenue vs. Vanity Metrics in B2B Startups | 0 | 0 | 0 | 0 | Tom explains the difference between vanity metrics like GMV and core B2B metrics like pure revenue using examples from YC batches. | |
| Net Burn Rate, Runway, and Financial Transparency | 0 | 0 | 0 | 0 | Tom breaks down net burn rate, runway calculations, and visual cohort retention layer cakes without any interviewer interaction. | |
| Net Dollar Retention (NDR) for B2B SaaS Startups | 0 | 0 | 0 | 0 | Tom walks through mathematical examples and benchmarks for Net Dollar Retention (NDR) in B2B SaaS companies in a continuous lecture. | |
| Gross Margin, Unit Economics, and Sustainable Scaling | 0 | 0 | 0 | 0 | Tom discusses gross margin, OpenAI API cost pitfalls, and the danger of blitzscaling negative unit economics using Monzo and Uber as examples. | |
| Summary, Conclusion, and Final Recommendations | 0 | 0 | 0 | 0 | Tom recaps the core lessons of the lecture and delivers final takeaways on balancing metrics with customer conversations. |
Statements from this episode (13)
Blomfield: Command of core metrics strongly differentiates founders to investors
“It's really easy to tell founders who are in command of their metrics versus founders who aren't. And it's really impressive when founders can talk about what percentage of their signups are DAU or WAU or what the annual revenue per user is. And we'll go into …”
Blomfield: Early Startups Lack Scale to Split-Test Minor UI Tweaks
“Making buttons red or green, that's not really something you have the scale to split test until you're really at the size of Google or Facebook.”
Blomfield: Debating Metric Definitions Is Worse Than Having No Metrics
“Constant arguments about what your key metrics are even worse than having no metrics at all.”
Blomfield: Monzo Defined Weekly Active Users as Transacting Weekly
“So a weekly active user at my old company, Monzo, was someone who transacted, who made a financial transaction at least once a week.”
Blomfield: B2B Startups Must Prioritize Revenue Over Gross Transaction Value
“And so almost always, especially for B to B companies, your key metric should be revenue. If you pick another number, take gross transaction value, you'll find that your employees, and eventually you might start optimizing for that number.”
Blomfield: Missing burn or runway in investor updates signals something to hide
“Those three numbers, revenue, burn rate, and runway are absolutely crucial to include. And if they're not at the top of your investor updates, honestly, I always assume this founder has something to hide.”
Blomfield: Retention flattening at 20% beats higher retention decaying to zero
“And it almost matters that they flatten out at any point as opposed to a high point. You know, I take a 20% retention that flattens out over a higher retention initially that goes to zero.”
Blomfield: Early-stage B2B SaaS startups should target 125% to 150%+ NDR
“The final thing, as a benchmark, any early stage B to B SaaS company should be looking at net dollar retention well above 100%. This is for several reasons. First of all, you've probably underpriced your product with your first launch. So you might charge 10,0…”
Blomfield: 110% to 120% NDR is a good benchmark for mature SaaS companies
“For mature companies in the same range, 110%, 120% is pretty good net dollar retention.”
Blomfield: Sub-100% NDR means fixing churn before increasing sales spend
“If your net dollar retention is below 100%, especially for enterprise B to B SaaS, something is wrong. You are churning off customers. They don't love the product. And I would invest in fixing that. Talking to customers and figuring out why they're churning of…”
Blomfield: AI startups relying on OpenAI credits face severe margin shocks
“Just because you're getting free credits doesn't mean that that's a cost that doesn't exist. It just means you're hiding it for the moment. So companies that hide behind OpenAI credits and claim that they've got these huge, huge gross margins have a nasty shoc…”
Blomfield: Monzo lost £30–£40 per user initially before turning profitable
“Monzo is an online bank in the UK, and for our first half a million customers or so, we were losing money on every customer, 30 or 40 pounds per customer. We scaled to more than half a million of those customers. It costs a lot, but we had a plan to turn it ro…”
Blomfield: Founders must fix negative unit economics before scaling
“So if you start with negative unit economics, you really, really have to have a plan to fix them. And I would really advise you don't scale your customer base. You don't try and grow as quickly as possible whilst you have negative unit economics. You fix them …”