Rest energy of the electron - calculation discrepancy

[Freezeline]

When I use E=mc2 to calc. the rest energy of an electron, I get .512Mev not .511Mev. I am using 9.109x10-31 kg for the rest mass of an electron and 2.9979x10^8 m/s for the speed of light in a vacuum.
Can anyone tell me why there ís a discrepancy between my results and the accepted answer?

 

[Nugatory]

What are you using as the conversion factor between Joules and Mev?

 

[Freezeline]

You found my mistake. I was using 1.6x10-19joules equals 1 eV, instead of 1.602x10-19.
Thank you for your help.