Dustin Johnson made the complicated world golf ranking calculations simple on Sunday, vaulting to number one with a convincing victory in the Genesis Open.

"I don't really understand it," he said of the math involved in determining the game's top player "but I can read the 'one-two-three'. I guess that's all that matters."

All week at Riviera Country Club, Johnson shied away from talk of ending Jason Day's 47-week run atop the rankings -- a possibility that also depended on where Day finished.

"I was coming in here to put myself in a position to win and I did that -- and I played really well," said Johnson, who led by as many as nine strokes on Sunday en route to a five-shot victory with a 17-under par total of 267.

"If I get to number one winning the golf tournament, then obviously that's even a bonus."

After a heartbreaking history of near-misses in major championships, Johnson broke through at the US Open at Oakmont last year. His victory on Sunday was his fourth since June.

"Obviously winning the US Open in the summer kind of gave me a little bit of a boost with confidence with my game," he said. "It was big for me ... to finally win one.

"Today kind of felt a lot like how I was playing this past summer, finally getting back to where I was, driving it really well."

But the rankings are tight at the top -- right down to number six Jordan Spieth. Rory McIlroy and Henrik Stenson -- ranked second and fourth coming into the week, were absent, but number five Hideki Matsuyama also had a mathematical chance to topple Day at Riviera only to miss the cut.

"Number one can toss and turn in the coming weeks a lot of times if the guys keep playing well," Day said.

The Australian also noted that the number one ranking brings some added pressure, although he thought Johnson had the wherewithal to cope with that.

"I think he's going to do just fine," Day said. "I think he's won every single year that he's been out here. That's the formula -- you've got to win as much as you can."

Johnson said he hadn't considered whether becoming number one could prove a burden.

He'd been too busy celebrating his victory on the 18th green with two-year-old son Tatum. Days earlier, his fiancee, Paulina Gretzky, announced on Instagram that the couple are expecting their second child.

"I've only been number one for about 30 minutes," Johnson said. "Ask me in a couple of weeks."