NEW YORK — Brian Spaly’s quest for the perfect pair of pants led him and former roommate Andy Dunn to start a Web-only clothing company that wants to sell men’s trousers that fit — without the need for fitting rooms.

Business is good for their company, Bonobos Inc., though it’s too early to tell whether the startup can achieve the heights of another online apparel store with a remarkably similar beginning.

That company is Zappos, which Amazon .com Inc. recently snapped up in a $850 million deal. A decade earlier, Nick Swinmurn spent a fateful hour schlepping around a San Francisco mall looking for the right pair of shoes. When he didn’t find them, he went on to create Zappos.com Inc., a Web-only shoe retailer known for its broad selection of items, generous return policy and quirky culture.

Bonobos, named after the endangered ape, was likewise born out of a do-it-yourself project. Spaly, like many men, had a hard time finding pants that fit well despite his athletic build.

Mass-market pants, the kind you find at chain stores, are often baggy and frumpy, with lots of extra fabric around the thigh, Spaly says. He calls this “khaki diaper-butt.” High-end designer pants, meanwhile, are expensive and too tight, cut for pencil-legged fashionistas and runway models.

Bonobos aims for the comfy middle ground. Its pants, most of which cost $118, have a curved waistband, less fabric in the thighs than the frumpy pants its founders frown on, and a slight boot cut. They come in classic men’s colors like khaki, blue and gray, but also in orange, pale lavender and jungle green with bright flowers.

The company is so confident in its designs it accepts pants for return, free of postage for the buyer, no matter when they were bought and even if they’ve been washed, worn and hemmed.

That is yet another parallel with Zappos, which accepts returns, postage paid, for 365 days. Both offer free domestic shipping. Such policies, along with impeccable costumer service, are crucial for Web-only retailers looking to sell things that people are used to trying on in brick-and-mortar stores.

Bonobos, which doesn’t sell women’s clothing, operates under the assumption that men don’t like shopping. Bonobos encourages customers to order pants in several sizes and return the ones that don’t fit.

Mitch McCann, an Army officer stationed in Iraq, bought a pair last November. A Web ad caught his eye, highlighting Bonobos’ no-questions-asked, free return policy.

“I checked out their site, almost just to find the fine print with the loopholes,” McCann, 34, wrote in an e-mail from Iraq, where his job often has him wearing civilian clothes. “I was very surprised by what I found. … This was a company that really just wanted to make awesome pants.”

The lone downside, he says: Bonobos pants need hemming, because the company believes that ensures a custom fit for each buyer. McCann wishes Bonobos would let customers specify an inseam length and wear the pants out of the box. For now, he has them safety-pinned, and plans to see a tailor when he returns to the U.S.

Bonobos pants were born when Spaly used his girlfriend’s sewing machine to rip apart and hem his store-bought pants. As a business student at Stanford University in 2005, he focused on pants even as his classmates turned their eye toward technology. He was soon selling the pants to classmates.

After Dunn signed on as a business partner, the pair, now in New York, launched Bonobos out of Dunn’s apartment in October 2007. Dunn, 30, is CEO and Spaly, 32, serves as chairman.

Neither founder has a fashion background, and the Silicon Valley roots of the company influence the way it is run. All of Dunn and Spaly’s 18 employees have equity stakes, including the customer service reps — who are called “ninjas.”

Bonobos uses Twitter and Facebook to get feedback on designs. And like any Web startup, Bonobos relies heavily on word of mouth.

Dunn and Spaly voice admiration for Zappos, which prides itself on its 10 core values — including “do more with less” and “create fun and a little weirdness.” They even hired two former Zappos staffers — one now serves as vice president of engineering. Zappos declined to comment for this story.

Last year Bonobos reaped $1.6 million in revenue, and this year it expects two to three times that, though the company hasn’t turned a profit.

The company operates out of a tightly packed Manhattan office and is slowly expanding, having diversified into shorts, swimming trunks and polo shirts. (Zappos also went beyond shoes and now sells clothes and accessories such as handbags.)

Whether Bonobos takes off with the masses may depend on whether it can introduce some cheaper pants.

Troy Hooper, a 27-year-old financial analyst from Minneapolis, has bought 11 pairs from Bonobos in the past year or so, after losing 40 pounds. He admits to getting some “funny looks” when he tells friends how much the pants cost.

“It’s more money,” he says, “than I have ever paid for a pair of pants in my life.”