Vibe Code an ROI Calculator in 120 Minutes That Closes Deals
A Step-by-Step Guide to Building An ROI Calculator That Your Sales Team Will Use and LOVE!
I sat down to record this week’s video, hit record… and about halfway through realized it just wasn’t working. The build itself was solid, but explaining it on camera felt slow, clunky, and honestly more boring than it deserved.
So, I decided to pivot and turn this into a written piece. It’s a step-by-step guide and something you can actually follow and ship from. I’m actually very happy with the way this came out because I was able to add a lot of extra detail that I either couldn’t or would have forgot to mention in the video itself.
If you like this format, I can do more of these. If you prefer video, tell me that too. Feedback is always welcome.
This week’s Stack:
1 deep dive: Build an ROI calculator with Lovable
1 prompt: Audit competitor conversion paths like a CRO
1 tool: Generate fast, high-quality images without friction
3 resources: Sharp predictions, conversational ad tech, real GTM lessons
3 jobs: Product marketing, growth, and AI-native roles worth a look
Let’s go!
Deep Dive: Vibe Code an ROI Calculator
You know your product delivers ROI. You have the case studies, the proof points, the slide that makes executives nod. But when a buyer sits down to make a purchasing decision, there’s still a gap between hearing your value and believing it applies to them.
That gap is where deals stall.
But an ROI calculator can help close it. It lets buyers run the math themselves. When someone plugs in their pipeline, win rate, ACV, and team capacity, they stop evaluating your product as “interesting” and start believing that it can work for them.
The practical reason this matters right now is that building calculators like this used to require engineering time, design support, and weeks of coordination. With Lovable in 2026, you can design, build, and QA a real calculator in a single afternoon.
This post walks through exactly how to do it, using Lovable to build the app (UI, logic, and validation), Supabase to store every calculator run, and HubSpot to create leads and pass results to sales. By the end, you will have everything you need to ship your own calculator this week. In fact, you can do it in one afternoon if you block off 120 minutes. Seriously.
Why ROI Calculators Beat Your Best Case Study
Most marketing assets ask buyers to imagine a better future. Case studies say “Company X got these results.” Whitepapers say “Here is why this approach works.” Both require the buyer to make a mental leap: “Would this work for me?”
ROI calculators let buyers test whether your value story holds up under scrutiny with their actual numbers. Instead of trusting your slide, they see their own situation reflected back.
This is why calculators work so well in the middle and late funnel. They reduce ambiguity at the decision point, give champions something tangible to share internally, create sales context (”they said payback is under 3 months”), and they shift the conversation from features to economics.
Notice that we’re treating this ROI calculator like a decision-support tool. Yes, they can be a great lead magnet, but they can be so much more that will help you move the revenue needle. When you do, it becomes one of the highest-leverage GTM assets you can build (and your sales team will love you for it).
What You Are Building
Before you open Lovable, you need a clear picture of what you are making. The calculator is a single-page web app that collects 5 to 6 numeric inputs from the user, each with sensible defaults and helpful tooltips so people can move quickly even if they do not know their exact numbers.
The app includes a scenario toggle that lets users switch between Conservative, Base, and Aggressive assumptions. This matters because buyers are skeptical of optimistic projections. Giving them control over the assumptions builds trust and lets them stress-test the numbers themselves.
The experience shows a teaser result before the email gate, typically a single compelling number like annual impact or payback period. This gives users a taste of value before you ask for their email. After they submit, they see the full breakdown.
The full results display these metrics:
Annual Impact ($)
Annual Cost ($)
Net ROI ($)
ROI Percent
Payback Period (months)
Below the results, include an “Assumptions Used” section that shows the defaults and scenario multipliers. Transparency here is what separates a trustworthy calculator from a marketing gimmick.
On the backend, every calculator run gets stored in Supabase with inputs, outputs, scenario, timestamp, and email. The app also creates or updates a contact in HubSpot with the same data so your sales team can follow up with context.
Define What ROI Actually Means for Your Product
This is the step most people rush, and it is why most ROI calculators feel fluffy. If you cannot explain your value equation in one sentence, your calculator will not land.
Start by picking a primary value driver. Revenue lift works if your product increases win rates, conversion rates, deal sizes, or pipeline volume. Cost savings works if you reduce hours spent, consolidate tools, or eliminate contractor spend. Risk reduction is less common but can work if you can quantify it.
Once you pick your angle, write out the value equation in plain language. For revenue lift, it might be: “If we increase win rate by X points, you generate $Y more revenue annually.” For cost savings: “If we save X hours per week per rep, you save $Y annually in labor cost.”
This sentence becomes your calculator’s logic. Everything else flows from it.
Choosing Your Inputs
Stick to 5 or 6 inputs at most, and make sure each one feeds your value equation directly. More inputs usually mean more friction and more drop-off.
If you are building for pipeline and revenue lift, your inputs might include monthly opportunities (or monthly qualified leads), current win rate as a percentage, average contract value, and expected improvement (like +3 win rate points). Sales cycle length is optional but can add nuance if your product shortens time to close.
If you are building for time and cost savings, consider number of reps or marketers, hours saved per person per week, fully loaded hourly rate (or a salary band the user can select), and weeks worked per year. Adoption rate is optional but helpful for realistic projections.
Default values matter more than you think. Most users do not know their exact numbers, and they will abandon the calculator if they have to go find them. Add defaults that are conservative enough to trust, realistic enough to demonstrate value, and easy enough to avoid friction. A good default lets someone complete the calculator in under 60 seconds.
A Real Example to Validate Your Math
Before you build, work through a concrete scenario by hand. This gives you a test case to validate your calculator outputs once Lovable generates the app.
Here is a mid-market SaaS scenario for revenue lift via win rate improvement. Assume the company has 80 monthly opportunities, a current win rate of 22 percent, an average deal size of $14,000, a win rate improvement of +5 percentage points from your product, and an annual product cost of $36,000.
Now run the math. Annual opportunities equal 80*12, which is 960. Additional wins equal 960*0.05, which is 48 deals. Incremental revenue equals 48*$14,000, which is $672,000. Net impact equals $672,000 – $36,000, which is $636,000. Payback period equals $36,000/monthly impact ($672,000/by 12), which comes to about 0.64 months.
Your calculator does not need to show every line of this math, but it must produce outputs consistent with these kinds of scenarios. If the numbers do not match, fix the logic before you ship.
Designing the Experience (Product, Not Spreadsheet)
Your UX goal is simple: users should feel like it’s easy to complete and hard to misunderstand. In other words, this should NOT feel like a spreadsheet.
The Layout
A single-page flow works best. Start with a headline and one-line promise that tells users what they will get. Follow with your 5 to 6 input fields, each with defaults. Add the scenario toggle (Conservative, Base, Aggressive). Show teaser results with one compelling number. Gate the full breakdown behind email. After submission, display all metrics plus a brief explanation of each. Include the assumptions used section showing defaults and scenario multipliers. Optionally add a “Send me results” or “Book a walkthrough” CTA at the bottom.
Input Field Best Practices
Use tooltips that say something like “If you are not sure, use our default.” Add light validation such as “Must be between 0 and 100” for percentage fields. Keep labels plain and avoid marketing language. Do not force precision. Rounded estimates are fine for this purpose.
Build It in Lovable (The Step-by-Step)
This is where January 2026 Lovable shines. It is not just generating UI. It helps you think through the logic, build the app, and QA the output.
Step 1: Start With This Prompt
Copy and paste this into Lovable:
Build a single-page ROI calculator web app for a B2B SaaS product. Requirements:- 5-6 numeric inputs with helpful defaults and tooltips- Scenario toggle: Conservative/Base/Aggressive that changes 2-3 assumptions- Results include: Annual Impact ($), Annual Cost ($), Net ROI ($), ROI %, Payback Period (months)- Show teaser results before email gate, then full results after email submission- Include an “Assumptions used” section listing defaults and scenario multipliers- Validate inputs (no negatives, handle blanks, handle extreme values gracefully)- Mobile-friendly, clean UI- Store each run to Supabase: inputs, scenario, outputs, timestamp, email- Create/update a contact in HubSpot with email + calculator outputsAsk me clarifying questions if anything is missing before generating.
Step 2: Answer Lovable’s Clarifying Questions
Lovable will ask questions about your exact inputs, what assumptions change by scenario, how the annual cost works (fixed versus variable), whether you want to model gross margin or top-line revenue, and when the email gate appears.
Answer in short bullets. For example: “Inputs: Monthly opps, win rate, ACV, win-rate lift, annual cost. Base scenario: +5 points win rate. Conservative: +3 points. Aggressive: +8 points. Gate after teaser results.”
The more specific you are here, the closer Lovable gets on the first try.
Step 3: Generate V1 and Validate the Math First
Your first goal is correct logic. You can/should worry about building a beautiful page later. Run through a quick validation checklist before you worry about design polish.
Check that win rate handles 0 to 100 properly. Check that blank inputs default gracefully instead of breaking the calculation. Check that negative numbers are blocked. Check that payback period avoids divide-by-zero errors. Check that scenario toggles change outputs correctly. Use your hand-calculated example from earlier to verify the outputs match.
Only after the math is solid should you move on to styling and polish.
Connect Supabase
Supabase is what turns a cool page into a system. Every calculator run becomes a record you can analyze, segment, and act on.
Create Your Table
Create a table called roi_calculator_runs with the following fields:
For identifiers: id (uuid) and created_at (timestamp).
For user info: email (text).
For scenario: scenario (text) to capture whether they chose Conservative, Base, or Aggressive.
For inputs (all numeric): monthly_opps, win_rate, acv, win_rate_lift, annual_cost.
For outputs (all numeric): annual_impact, net_roi, roi_percent, payback_months.
If you want richer data for analysis, add optional fields like company, role, utm_source, utm_campaign, and utm_medium. These help you understand which channels and segments generate the highest-value calculator users.
Why Store Both Inputs and Outputs
Store both. Outputs are what sales uses for follow-up (”I saw you are looking at a 3-month payback”). Inputs are what you analyze later to understand your audience. If most users have 50+ monthly opportunities, that tells you something about your ICP. If most users select Conservative, that tells you something about trust levels.
Connect HubSpot to Turn Runs Into Pipeline
This is where ROI calculators become a pipeline machine.
Minimum Fields to Write
At minimum, write these to the HubSpot contact record: email, scenario selected, annual impact ($), payback period (months), and ROI percent. If you can also pass 1 or 2 key inputs like monthly opps and ACV, your SDR follow-up becomes eerily personal in a good way. Sales can reference the prospect’s actual situation instead of sending generic outreach.
Create a Note for Sales Context
Log a note or timeline event on the contact record. Something like: “Completed ROI Calculator. Estimated annual impact: $672K. Payback: 0.6 months. Scenario: Base.”
This changes sales outreach from “just checking in” to “following up on your math.” That context makes a difference in response rates.
QA to Make It Works and Users Will Trust It
This step is not optional. In 2026, buyers are trained to question AI-generated content, especially when it involves math. A calculator that breaks on edge cases destroys trust instantly.
Edge Cases to Test
Run through each scenario with the following test cases:
All defaults (baseline behavior)
All zeros (should handle gracefully, not break)
One zero at a time: ACV=0, win rate=0, etc.
Very high values (stress test the math)
Blank fields (should use defaults)
Negative numbers (should fail validation)
Win rate over 100 (should fail validation)
Very low ACV plus very high opportunity volume
Guardrails That Build Trust
Add guardrails that make the calculator feel credible. Clamp input ranges so win rate stays between 0 and 100. Show a warning on extreme numbers like “That is unusually high. Double check your input.” Include the assumptions used section so users can see exactly what drove the results. Round outputs to avoid false precision. Showing $672,341.27 feels like a lie. Showing $672,000 feels like an estimate.
Launch and Measure What Matters
Once it is live, you are not done. You are learning.
Metrics That Tell You If It Is Working
Track completion rate, targeting 40 to 50 percent. If it is lower, your inputs are creating too much friction. Track email gate conversion rate to see how many users find the teaser compelling enough to continue. Track drop-off by field to identify which specific input causes people to abandon. Track median payback period across all runs, because this becomes messaging you can use elsewhere. And track HubSpot contact-to-meeting rate for calculator users compared to your baseline lead sources.
The last metric is the one that matters most. If calculator leads convert to meetings at a higher rate than other sources, you have built something that moves pipeline.
The Math Does the Convincing
Most marketing talks at buyers and tries to explain value, but ROI calculators let buyers experience it in their own language, and more importantly, numbers that matter to them.
With how Lovable works today, building is no longer something reserved only for engineers. Lovable makes it a practical GTM activity you can ship this week, iterate next week, and benefit from for months. Build it once, refine it based on real usage, and let the math do the convincing.
Prompt of the Week: Website conversion path audit
I love spying on competitors. I don’t copy everything that they do, but I like to analyze what they’re doing to better understand their strategy.
This prompt helps you reverse‑engineer those journeys across competitor websites and turn what you learn into concrete tests for your own site. This prompt I borrowed from Kipp and Kieran’s Marketing Against The Grain Prompt of the Day.
Use Case: Analyze the conversion strategies and user journeys on competitor websites to identify best practices and opportunities.
You are a conversion rate optimization (CRO) specialist and user experience analyst. I need you to audit the conversion paths and tactics used on competitor websites.
COMPETITORS TO AUDIT:
[Competitor 1 URL]
[Competitor 2 URL]
[Competitor 3 URL]
MY WEBSITE (for comparison): [Your URL]
AUDIT REQUIREMENTS:
1. HOMEPAGE CONVERSION ELEMENTS
- Primary CTA
- Secondary CTAs
- Value proposition clarity
- Social proof
- Trust signals
2. NAVIGATION & USER JOURNEY
- Navigation structure
- Clicks to conversion pages
- Sticky CTAs
- Retention tactics
3. LEAD CAPTURE MECHANISMS
- Primary conversion path
- Lead magnets
- Email incentives
- Chat or chatbot
- Multi‑step forms
4. LANDING PAGE STRATEGY
- Dedicated landing pages
- Page structure
- Offer positioning
5. PRODUCT / DEMO EXPERIENCE
- Product presentation
- Self‑serve vs sales‑led
- Onboarding cues
DELIVERABLE:
- Conversion audit summary per competitor
- Comparative analysis
- Recommendations for my siteI’ve added this to my The Ultimate ChatGPT Prompt Library for B2B Marketing Leaders notion doc. Check it out for 60+ more prompts.
Know someone who might find this prompt useful? Share it with them!
Tool of the Week: Reve, a fast and fun image generation tool
This one’s simple. I first heard about Reve on Jason Lemkin’s SaaStr podcast and immediately started playing with it. I haven’t used it heavily for work yet, but I’ve been generating a lot of images for personal projects and creative experiments.
Reve makes it easy to spin up high‑quality visuals without overthinking prompts or settings. It’s fast, lightweight, and I love it for exploring ideas.
Try it: https://app.reve.com/
AI Resource Roundup
Kellblog Predictions for 2026: This ins is not strictly AI marketing, but Dave Kellogg is essential reading if you are a marketing leader and care about how SaaS actually works. I love prediction posts, and Dave’s is one that I look forward to every year.
Our approach to advertising and expanding access to ChatGPT: OpenAI announces they’re adding advertising in ChatGPT. There’s a lot of commentary around this, including one that I thought was great from 20VC (around the 40 min mark here), but I just wanted to give you the actual announcement straight from OpenAI.
AI in GTM: What Works, What Doesn’t, and How to Win in 2026: This was a good, practical conversation on where AI is delivering real GTM value today versus where it’s still hype. It’s my podcast, done in partnership with BenchmarkIt.
Hot AI Jobs
Lead Product Marketing Manager, AI at Sentry
Location: San Francisco, CA (Hybrid)
Pay Range: $200K–$215K
Location: Remote
Pay Range: Not Listed
Location: San Francisco, CA (On‑site)
Pay Range: $130K–$200K
If you’re in the U.S. and in the path of the storm this weekend, I hope you bundle up and stay warm. Looking at the forecast, it doesn’t look like it’s going to be above 12 degrees here in Colorado.
Make a nice cup of coffee and an ROI tool that brings in hot leads.
– Brandon
Brilliant. That line about the gap between hearing value and believing it applies to them is realy spot on. So insightful!