Started as a slime-brand spreadsheet at our kitchen table.

How this started

My wife was getting into slimes. Small-batch, hand-mixed, looking at starting her own slime brand. We’re both the kind of people who are always running the numbers on whatever we’re thinking about next, so before she invested time and money into it she built a spreadsheet to figure out whether it would actually pencil out. Materials, packaging, TikTok Shop fees, heat-pack costs for the summer months. The works.

I looked at what she’d built and thought it was a kind of cool. The more I thought about it, the more I realized: this same pattern would work for any DIY business someone was seriously considering. Could we model a food truck the same way? A cleaning service? A subscription box? A handmade candle brand? Turns out yes. Once you commit to building one model per vertical instead of pretending they’re all the same kind of business, it’s very doable.

That’s how StartupLenz started: one couple’s slime- brand spreadsheet, expanded into ten verticals (and counting) so other would-be DIY founders can see what their idea actually costs to start, before they jump.

First product

This is the first product I’ve ever shipped to real users.

I’m not a serial founder with a backlog of SaaS ideas waiting for the right moment. I had a problem at my kitchen table — a partner who wanted to know if a real business would pencil out — and a spreadsheet she’d built that I thought was useful enough to expand. So I expanded it.

I’m saying it out loud because I think it matters. Most cost-calculator tools you’ll find on the web are built either by big SaaS shops trying to fill an SEO niche, or by no-name affiliate operations trying to capture a download for an email list. The math in them is often whatever the contractor pulled from a 2019 blog post.

StartupLenz isn’t that. It’s a real person, living with a partner who actually runs the kinds of businesses we model, building the tool we both wished existed when she sat down to do the slime math. If it gets to ten thousand users, it’ll still be that. If it gets to ten, it’ll still be that.

The problem we’re solving

Every business-cost calculator I’d ever opened was either (a) a generic spreadsheet template that treated a candle brand and a food truck like the same business, or (b) a polished SaaS tool built for VC-backed startups, where you’re modeling $50M ARR and 200 employees by year three.

Neither was useful when the actual question was:“If I sell slime on TikTok Shop, with my own packaging and a heat-pack budget for July, do I make money or do I burn out?”

That question has a specific, knowable answer. Marketplace fees are public. Material costs are knowable. Labor minutes are measurable. The only thing missing was a tool that put those specific dials in your hand for your specific business and told you the truth in plain language.

The thing that makes this different: it’s alive

Most cost calculators, including the ones in business books and YouTube tutorials, are dead. They were built once with whatever data was current that year, published, and then they sat there. By the time you opened them, the platform fees had changed, materials had inflated, channel economics had shifted.

StartupLenz is built differently. The data under every vertical (default fee rates, average shipping costs, industry margin benchmarks, channel-mix splits) lives in our database, not hardcoded in a static spreadsheet. When Etsy bumps its fee, we update the default. When a major shipping carrier changes its rates, we update the default. When the average slime sell-through on TikTok Shop shifts, we update the default. Every vertical’s model engine is versioned in source control so changes are traceable, and the calculators stay accurate to what indie operators are actually navigating right now.

We built the living pathways: the database schema, the content management tools, the publishing pipeline. The calculators can keep up with the markets they describe. That’s the backbone. The user-facing sliders are just the surface.

What else makes StartupLenz different

Channel-aware modeling. Most calculators average your platform fees into a single percentage. StartupLenz splits revenue across the platforms you actually sell on (Etsy / TikTok Shop / your own site, depending on the vertical), applies the right fee structure to each slice, and shows you which channel actually pays you the most.

Vertical-specific inputs. Every input field exists because the data we’ve gathered shows it matters. We don’t include “office rent” if the business is normally run from a kitchen. We don’t include “website hosting” as a $50/month line item when Shopify already takes a cut elsewhere. The shape of the inputs matches how the business actually runs.

Written-take insights. The paragraph below your numbers is the most important thing on the page. It’s not a stock template, it’s an opinionated read of your specific numbers, generated by the vertical’s model engine. “Healthy 24.9% margin. Most slime brands at this tier reinvest into bigger drops + paid creator collabs to scale.” The kind of thing a friend who’d already done it would tell you.

Free forever, for real. The core calculators are free. No trial, no “upgrade to see your full report,” no email gate before you see the numbers. Sign in if you want to save plans across devices, but you never have to. We’ll add paid features eventually (alerts when a fee that affects your saved plan changes, multi-user access, sector benchmarks) but the core math will stay free.

What we won’t do

• We won’t sell your individual data. Aggregated anonymized benchmarks for future product features, maybe. Your specific plan, attached to your email, sold to a third party? No.
• We won’t fabricate testimonials. Every indie tool launches with three made-up Sarahs from imagined companies. You’ll see real testimonials here only when we have real ones.
• We won’t add features that aren’t decision-useful. Pretty charts that don’t change what a founder does next are noise. If we add it, it’s because someone we trust said it would have changed how they built their business.
• We won’t pretend to be a financial advisor. This is a planning tool. We’ll never have an affiliate relationship with a payment processor or platform we model, and we’ll never recommend specific brokerage products.

Where this is going

We’re always looking for the next category that makes sense to model. Service businesses are coming next: cleaning, lawncare, mobile auto-detail, beauty. After that, probably food & beverage outside the food-truck format (ghost kitchens, baked goods, micro-roasters). If you’re running a vertical we haven’t modeled yet and you’d be willing to share what actually drives your P&L, email us and we’ll prioritize yours.

How to reach us

Email hello@startuplenz.com. We read every message. Whether it’s “your math is off on the candle vertical here’s why,” or “you should model X next,” or just “this helped me decide not to start a business that would’ve lost money for two years,” we want to hear it.