Em         Am
Fills the air,
       G                 D
And I fall in love with you,
           Em
All over again,

Am
Ooh,
             G                   D
You're the light that feeds the sun,
        Em      Am
In my world, 
              G               D
I'd face a thousand years of pain
        Em   Am, G, D
For my girl.

................................................................

The same pattern is repeated throughout the song, you could change strumming 
patterns if it helps :)

Em, Am, G, D,

................................................................

[Pre-Chorus]
Out of all the things in life,
That I could fear,
The only thing that would hurt me,
Is if you weren't here,
Woah

[Chorus]
I don't want to go back
To just being one half of the equation
You understand what I'm sayin'?

Girl with out you I'm lost
Can't face this focus at heart
Between me and love
You're the common denominator, oh, oh, ohh, oh
You're the common denominator, oh, yeah, woah

[Verse]
Before your love was low
Now you're just my height, aye
We chase the game that would put
My cot in the side

Broken heart rise up to say
Love is alive
You and I would stand
To be multiplied, yeah

[Pre-Chorus]
Out of all the things in life,
That I could fear,
Uh
The only thing that would hurt me,
Is if you weren't here,
Woah

[Chorus]
I don't want to go back
To just being one half of the equation
You understand what I'm sayin'?

Girl with out you I'm lost
Can't face this focus at heart
Between me and love
You're the common denominator, oh, oh, ohh, oh
You're the common denominator, oh, yeah, woah

I'm never ever not, justin bieber I love you
Without your touch,
Every kiss that you give,
It gives me heart,
And to all the heart it can,
Jealous females hate it,
I'ma hold it down for you,

For you, woah, oh woah,
Common denominator,
Oh, yeah, woahh,
I don't wanna to go back,
Half of the equation, woah woah yeah,
Common denominator
Oh, oh, oh, oh,
Common denominator
Oh, yeah, woah