Grenade is the second track off his debut album Doo-Wops & Hooligans, which is set to be released on January 17, after being moved forward due to high demand.
Mars is currently outselling Jessie J's Do It Like A Dude and Rihanna’s What's My Name which is currently holding the number one spot.
His track Just the Way You Are went to number one twice last year.
The other songs making up the top five are Lights On by Katy B and Adele's latest single Make You Feel My Love.
Over in the midweek album chart Adele's, despite being three years old, is currently sitting at number five.
The top two albums look set to remain unchanged, with Rihanna clinging on to the top spot and Plan B settling for second.
Ellie Goulding’s album has climbed the charts four places to number four, while Cee Lo Green's album The Lady Killer rises one place to number three.
Female First- Rachael Patan
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