3M's 15 percent rule gives staff free time — Post-it Notes are born

In 1948, 3M president William McKnight formalized a culture where researchers could use part of their workweek for side projects, no matter how far from their assigned work. The rule was deliberately informal — more permission than process — and sat alongside 3M's demand that 30% of each division's sales come from products less than four years old.

Let employees spend up to 15% of work hours on projects outside their job description, and let promising ones grow into products.

3M treated the 15% as permissive culture rather than tracked hours: Spencer Silver tinkered with an adhesive that stuck lightly without bonding, Art Fry combined it with his need for a bookmark that would stay in a hymnal, and 3M let the pair develop the note, trial it across headquarters, launch it as Press 'n Peel, then sample it across Boise — where 90% of people who tried it said they'd buy it.

Post-it Notes became one of the best-selling office products ever, available in more than 150 countries. The same 15% culture had already produced Scotch tape, and Wired's 1998 profile reported that 3M still expected 30% of each division's sales from products under four years old — the rule later became the template for Google's 20% time.

The 15 percent rule is 3M's oldest and most copied management invention. From 1948, under president William McKnight, the company let its scientists spend up to 15% of their work hours on projects entirely outside their job descriptions — an informal, unwritten permission rather than a tracked program. As one scientist told Wired in 1998, 'you can feel it right down to your toes.'

The rule's proof came in the 1970s. Spencer Silver had discovered an adhesive with microspheres that stuck lightly and peeled away cleanly, but spent years unable to find a use for it. Art Fry, frustrated that paper scraps kept falling out of his church choir hymnal, paired Silver's adhesive with his bookmark problem and invented the sticky note. 3M supplied the notes across its own headquarters, employees adopted them as a new way to communicate, and the product launched nationwide in 1980 as Post-it Notes.

What made it a work idea rather than a lucky accident was the system around it: 3M coupled free time with a standing requirement that 30% of each division's sales come from products less than four years old, and rewarded 15%-time successes — including an Innovator Award created in 1997. The practice outlived its inventors, and Post-it Notes now sell in more than 150 countries.

Unstructured time is cheap for a company to give but nearly impossible to buy later — ideas die without a sanctioned place to grow.

15% time created collisions: Silver's stray adhesive met Fry's everyday annoyance, which a product-owner culture could turn into a category.

Pairing free time with a sales-from-new-products target kept the freedom pointed at commercial outcomes.

Because the rule stayed informal, it scaled into 3M's identity instead of becoming another tracked program.

Giving people protected time to follow their curiosity costs little at the start, and the products that don't fit a job description are often the ones that open a whole new category.

Post-it Notes launched in US stores on April 6, 1980, reached Canada and Europe soon after, and by the 1990s were sold in more than 100 countries. Silver retired from 3M with more than 22 US patents; Fry was named corporate researcher, the company's top technical title. The 15 percent rule became the explicit model for Google's 20 percent time and remains the standard answer to how a company formalizes curiosity without strangling it — even as 3M's own divisions have occasionally fought it, which Wired documented when managers penalized off-mission work.