Every other list estimates market size. We counted the companies already taking payments, then counted how many solo builders got there first.
Every B2B SaaS idea list published this year works the same way. It names a category, asserts a market size, estimates an ACV, and moves on. The numbers are projections, and the better lists say so in the small print.
There is a more useful question, and it is answerable by counting rather than estimating: how many companies are already taking money in this category, and how many of them are one person? The first number proves buyers exist. The second tells you whether you are early or late.
We ran both across 3,876 B2B SaaS companies in the Stripe Index, our snapshot of 30,322 companies on Stripe’s public directory. The result is a ranking of B2B categories by measured gap rather than by claimed opportunity, and the top of it is not where the idea lists point.
The B2B-over-B2C advice is repeated constantly and almost never quantified. Here it is quantified. Among companies actually taking payments, classified by business model:
| Business model | Companies | Micro SaaS | Share | Avg buildability |
|---|---|---|---|---|
| b2c-saas | 2,671 | 911 | 34.1% | 5.38 |
| b2b-saas | 3,876 | 623 | 16.1% | 4.75 |
| api-infra | 228 | 26 | 11.4% | 4.32 |
| creator | 1,145 | 56 | 4.9% | 5.88 |
| fintech | 324 | 10 | 3.1% | 3.64 |
| marketplace | 1,952 | 37 | 1.9% | 4.47 |
| ecommerce | 4,511 | 47 | 1.0% | 4.42 |
| agency-services | 7,871 | 33 | 0.4% | 3.61 |
| nonprofit | 1,303 | 4 | 0.3% | 3.37 |
B2C SaaS carries 34.1% solo-builder density against B2B SaaS at 16.1%, so the average B2C category is twice as contested as the average B2B one. Note also that B2B SaaS has more companies, 3,876 against 2,671, so this is not a size artefact. More buyers, fewer competing solo builders.
The other line worth reading is agency-services: 7,871 companies, the largest business model in the whole index, at 0.4% micro SaaS. Services is where the money demonstrably is and where productised one-person software demonstrably is not. If you are weighing an agency against a product, that is the trade in one row.
One snapshot, queried live on September 21, 2026, plus a separate revenue set. Counts, not forecasts. The limitations are real and listed here rather than in a footnote.
| Source | What it is | Volume | Limitation |
|---|---|---|---|
| B2B SaaS population | Companies classified business_model = b2b-saas | 3,876 | A directory snapshot, not a census of B2B SaaS; classification is a model judgement from public positioning |
| Category | AI classification, operational taxonomy | 3,876 | Categories with fewer than 40 B2B companies are excluded as too thin to read |
| Micro SaaS flag | AI classification of one-person-scale products | 3,876 | Definitional edge cases; read the distribution, never one label |
| Buildability | AI 1-10 feasibility rating | 3,876 | Apparent difficulty from a public page, not measured engineering effort |
| Agentic flag | AI classification of stated agent capability | 3,876 | Detects claims, which lag and sometimes lead actual shipping |
| Median MRR | Revenue-verified products, categories with 25+ reporting | 8,699 set | Different taxonomy from the Stripe Index, so revenue mapping is directional; set skews indie so medians run low |
A gap is a category with enough companies to prove buyers exist and a solo-builder share well below the 16.1% B2B average. These six qualify.
| Category | B2B companies | Micro SaaS | Share | Buildability | Agentic |
|---|---|---|---|---|---|
| crm | 237 | 14 | 5.9% | 4.6 | 66 |
| security-identity | 106 | 7 | 6.6% | 4.3 | 17 |
| health-medical | 80 | 6 | 7.5% | 3.8 | 4 |
| subscription-management | 118 | 10 | 8.5% | 4.6 | 13 |
| ecommerce-platform | 120 | 11 | 9.2% | 4.5 | 12 |
| accounting-bookkeeping | 94 | 9 | 9.6% | 4.7 | 9 |
| B2B average | 3,876 | 623 | 16.1% | 4.75 | — |
CRM is the standout: the second-largest B2B category at 237 companies, with the lowest solo-builder share at 5.9%, roughly a third of the B2B average. It is not empty because nobody wants CRM. It is empty because CRM means data migration, integrations, permissions and support, which is the work that does not get done in a weekend.
That is precisely why the gap is durable. A category a solo builder can enter in a weekend is a category a hundred other solo builders can enter next weekend. Buildability tells you which is which: the gap categories average 4.4 against 5.1 for the contested ones below. The difficulty is the moat.
Health and medical is the extreme version at buildability 3.8 and 7.5% density. Compliance is the barrier, and compliance is also the reason the eventual incumbent keeps its customers.
The mirror image. These categories sit well above the 16.1% average, which means the idea is not novel and the race has a head start on you.
| Category | B2B companies | Micro SaaS | Share | Buildability |
|---|---|---|---|---|
| scheduling-booking | 214 | 50 | 23.4% | 5.3 |
| marketing-automation | 105 | 24 | 22.9% | 5.1 |
| ai-tools | 309 | 65 | 21.0% | 4.8 |
| lead-generation | 148 | 31 | 20.9% | 5.1 |
| invoicing-billing | 196 | 40 | 20.4% | 5.1 |
| events-ticketing | 79 | 16 | 20.3% | 5.3 |
| seo-analytics | 82 | 15 | 18.3% | 4.9 |
Scheduling and booking is the most contested B2B category at 23.4%, four times the density of CRM, on 23 fewer companies. Every one of these traps scores 4.8 or higher on buildability. That correlation is the whole lesson: the easier a category is to enter, the more crowded it already is, and the less your entry means.
AI tools deserves a note because it is the largest B2B category at 309 companies. It is crowded at 21.0%, though noticeably less crowded than it is on the consumer side, where AI tools reaches 50.9%. B2B AI tooling is contested. B2C AI tooling is saturated.
Gap analysis is only half the picture. A category can be empty and worthless. Cross-referenced against revenue-verified products, the B2B-leaning categories occupy the top of the table.
| Revenue category | Products reporting | Median MRR | p90 MRR | Maps to |
|---|---|---|---|---|
| Sales | 38 | $640 | $14,463 | crm, lead-generation |
| Marketing | 213 | $276 | $10,495 | marketing-automation, seo-analytics |
| Recruiting & HR | 42 | $168 | $4,746 | hr tooling |
| SaaS (general) | 353 | $156 | $6,398 | horizontal B2B |
| Analytics | 87 | $77 | $6,953 | data-analytics |
| Developer Tools | 165 | $68 | $3,506 | api-infra, security-identity |
| Productivity | 223 | $46 | $639 | project-management, workflow |
Sales carries a median MRR of $640 and a p90 of $14,463, the strongest pair in the table, from only 38 products reporting revenue. Both categories that map to it, CRM at 5.9% and lead generation at 20.9%, are worth contrasting: same revenue destination, very different levels of competition. CRM is the underbuilt route to the best-paying outcome.
Productivity is the counterexample that should end a lot of project plans. 223 products, a $46 median, and a p90 of $639. There is no tail. Winning that category earns roughly what being median in Sales earns.
Across all 30,322 companies, only 3.82% carry an agentic flag. Inside B2B SaaS the concentration is an order of magnitude higher, and it clusters in specific rooms.
Read CRM again with that number attached. 5.9% solo-built and 27.8% agentic: the incumbents are actively rebuilding the category around agents while solo builders have not arrived. That is the least comfortable and most interesting cell in this research. The window is open and it is being closed by funded companies, not by other indie founders.
Combining gap, revenue destination and agent activity, four B2B directions survive all three filters.
Everything on that list is boring, and that is the point. The categories that sound exciting are the ones at 21% to 23% density. Once you have picked a room, the next question is what specifically to build inside it, and that comes from the complaints: SaaS ideas backed by real pain points works at that level, and the cross-category view covers how the same test applies outside B2B.
By measured gap, CRM and sales tooling. CRM is the largest B2B category with the lowest solo-builder density: 237 companies and only 5.9% micro SaaS against a 16.1% B2B average, and it maps to the highest-paying revenue category at a $640 median MRR.
Yes, by roughly half. 16.1% of B2B SaaS products are one-person businesses against 34.1% of B2C SaaS. B2C SaaS is the most crowded business model for solo builders in the index, at 5.2 times the 6.6% overall baseline.
Scheduling and booking at 23.4%, marketing automation at 22.9%, AI tools at 21.0%, lead generation at 20.9%, invoicing and billing at 20.4% and events ticketing at 20.3%. All six sit above the 16.1% B2B average.
CRM at 5.9%, security and identity at 6.6%, health and medical at 7.5%, subscription management at 8.5%, ecommerce platform at 9.2% and accounting and bookkeeping at 9.6%.
It depends on category more than on execution. Sales carries the highest median MRR at $640 with a p90 of $14,463, Marketing follows at $276, and Productivity sits at a $46 median with a $639 p90.
They are concentrated in the categories with the biggest gaps. Within B2B SaaS, 39.4% of customer support companies and 27.8% of CRM companies are agentic, against 3.82% across the whole index.
Agency services is the largest business model in the index at 7,871 companies and 0.4% micro SaaS. Services is a proven way to get paid and a poor fit for productised one-person software. B2B SaaS at 3,876 companies and 16.1% is the productised path.
The Stripe Index, an AI-enriched snapshot of 30,322 companies on Stripe’s public directory filtered to 3,876 B2B SaaS companies, plus our revenue-verified set of 8,699 products. Queried live September 21, 2026. Limitations are in the methodology table above.
BigIdeasDB Research. (2026). B2B SaaS Ideas: 3,876 Companies Taking Payments, Ranked by Gap. BigIdeasDB. Retrieved from https://bigideasdb.com/b2b-saas-ideas