Jason Day becomes world number one

Day claimed his fourth victory in six starts by winning the BMW Championship by six shots on Sunday.

FILE: Jason Day claimed his fourth victory in six starts after winning the BMW Championship by six shots on Sunday. Picture: US PGA/Facebook.

LAKE FOREST, ILLINOIS - Jason Day claimed his fourth victory in six starts and surged to the world number one ranking after going wire-to-wire to win the BMW Championship by six shots on Sunday.

The Australian closed out his tournament with a two-under-par 69 to finish at 22-under 262 at Conway Farms, six clear of American rookie Daniel Berger (69) in the third of the PGA Tour's four FedExCup playoff events.

American Scott Piercy (70) was third at 15-under with Rickie Fowler (69), Rory McIlroy of Northern Ireland (70) and JB Holmes (68) sharing fourth at 14-under.

"The way I feel about my game, confidence level has been the highest I've ever had in my entire life," Day said.

"Its been an amazing kind of run for me, and now it just tops it off even better to get to number one in the world.

"I felt a lot of pressure over the last two days, especially today just knowing I had a six shot lead.

"Yesterday and today were probably the toughest rounds I've ever had to play in my entire life."

It is the seventh tour win for Day, the fifth of the season after winning the Farmers Insurance Open, the Canadian Open, his maiden major at the PGA Championship and the opening playoff event, The Barclays, prior to this triumph.

He led by as many as seven and by no less than four in the final round and faced no serious challenge as he played conservatively throughout.

Day becomes the third Australian to reach world number one, following Greg Norman and Adam Scott.

"Knowing that right now there's no one on this planet that's better than me, that's pretty cool," Day said.

"That out of all the golfers that are in the world playing right now, that I'm the best.

"It's such a good feeling."

He now heads to the 30-man, season-ending Tour Championship in top spot on the FedExCup points list, ensuring a win at East Lake Golf Club would see him claim a $10 million bonus.

Masters and US Open champion Jordan Spieth, Fowler, Henrik Stenson of Sweden and Bubba Watson will also control their fate next week in Atlanta by holding spots in the top five of the points list.

Harris English and Kevin Na will join them at the Tour Championship after they made clutch birdies on the 72nd hole while Piercy and Berger also fought their way in from outside the 30 to get to East Lake.

Daniel Summerhays, Russell Knox, Ben Martin and Jason Bohn lost their places in the top-30.

A trip to the Tour Championship also brings invitations to the opening three majors of 2016.