Heidi Zak

Why is it this hard to find a bra that fits?

In 2013, Heidi Zak was getting ready for a holiday party at Google when she realized she didn’t own a single bra that actually fit.

She ran to a store, tried on a few, and settled for one that was uncomfortable but “good enough.”

Sounds familiar?

That’s when it hit her: bras are not designed for “real” bodies.

So she left her job in advertising at Google.

Teamed up with lingerie designer Ra’el Cohen.

And co-founded ThirdLove with her husband, David Spector.

She invited 100 women from Craigslist to photograph themselves in fitted tank tops over their bras.

Then used the photos to build a prototype bra and a mobile app to measure fit.

She found that 37% of those women didn’t fit into standard cup sizes.

So she launched the first-ever half-cup sizes.

In early 2014, she manufactured the first line in Mexico.

The result? Disaster.

Shipping costs crushed margins.

She lost $400,000 in investment capital.

So she moved production to China.

Meanwhile, she spent over a year perfecting just two products: the T-shirt Bra and Full Coverage Bra.

Then came the “Fit Finder” quiz.

20+ million women have taken it.

It’s generated over 75 million data points on breast shape, size, and fit issues.

ThirdLove uses this data to design every product and optimize recommendations in real time.

In 2014, they were featured on Good Morning America.

Traffic surged. The site crashed. Completely.

Why? The team had custom-built their front and back ends… and it couldn’t handle the load.

Zak made the call to switch to a third-party web platform.

In 2017, she launched #BreakTheMold: a campaign
highlighting real women, not airbrushed models.

And in 2018, ThirdLove made Forbes’ Next Billion-Dollar Startups list, with a valuation of $750M.

Funding to date…
- Seed: $5.6M from NEA, Andreessen Horowitz, Yuri Milner, and Nas
- Series A: $8M in 2016
- Series B: $55M in 2019 led by L Catterton, with Susan and Anne Wojcicki and Tim Armstrong participating

In 2025, ThirdLove launched TempSync™, the first bra line designed specifically for menopause and hot flashes.

It uses volcanic minerals and activated carbon to regulate body temperature before overheating begins.

Today, ThirdLove has expanded into sleepwear, activewear, and underwear.

It’s the #3 online intimates brand in the U.S., behind Victoria’s Secret and Aerie.

And it’s donated over $50M in products to women in need.

Heidi is also an angel investor in 20+ female-founded companies including Bobbie, Olive & June, Our Place, and Cadence.