Contrary to the title of this article, there's no single right answer on how to split equity with a co-founder. But there are a few ways that you do want to avoid. Most founders ignore these until it's too late.
The default is 50/50 equal partners, especially with two engineers, previous co-founders, working on the idea before starting the company, etc. If a few people get together, feel like they're bringing equal weight, and are in this for five to ten years, they tend to split it evenly. That instinct is increasingly common: according to Carta's 2025 Founder Ownership Report, 45.9% of two-person founding teams divided equity equally in 2024, up from 31.5% in 2015.
But most founding teams still don't do it, and for good reason.
The negotiation looks different when one person originated the idea, spent years building domain expertise, and recruited a technical person to come build with them.
How unequal that share is depends on how dependent the company is on the technical hire vs. the person who really started it. If the CEO is the clear driver and the engineer was brought in to execute, you're probably looking at a 10-25% stake for the technical co-founder. If you recruited someone to come build your vision, the math looks different.
Carta's data backs this up: across all founding team sizes, there's typically a lead founder who receives an outsize share, and that person usually becomes the CEO.
Now, there is one thing that shifts the math, and that is salary. A technical co-founder drawing a full market-rate salary should expect less equity than one betting entirely on the outcome.
Most founding teams get it wrong when they spend all their energy on the split and none on control.
Early on, you typically don't have a board. And if you do, it's just the CEO. You don't usually see multiple founders on the board until an investor comes into play at Seed to take a board seat. That's by design. If you have a 50/50 split where both founders have equal voting control, and sh$t hits the fan, there’s no clean way out. In some cases, one founder may have founder share class terms that outline additional voting power. The CEO may not be able to legally remove a non-performing co-founder.
Carta data shows that roughly 23% of co-founders have departed their company by the three-year mark, and departure rates are accelerating in recent cohorts. Nearly one in four co-founders in VC-backed startups will face this within three years. Structure the company so it can survive if you two don't.
Voting control should sit with the CEO. Pair that with standard vesting (~four years) so equity is earned over time, rather than handed over at signing. A clean split means nothing without the governance to back it up.
