La energía es la capacidad de realizar el trabajo.Existe en varias formas, como cinética, potencial, térmica, etc. Se mide en Joules (J).
1 MJ = 10,000,000,000,000 erg 
1 erg = 1.0000e-13 MJ 
Ejemplo: 
Convertir 15 Megajoule a Ergio:
15 MJ = 150,000,000,000,000 erg 
| Megajoule | Ergio | 
|---|---|
| 0.01 MJ | 100,000,000,000 erg | 
| 0.1 MJ | 1,000,000,000,000 erg | 
| 1 MJ | 10,000,000,000,000 erg | 
| 2 MJ | 20,000,000,000,000 erg | 
| 3 MJ | 30,000,000,000,000 erg | 
| 5 MJ | 50,000,000,000,000 erg | 
| 10 MJ | 100,000,000,000,000 erg | 
| 20 MJ | 200,000,000,000,000 erg | 
| 30 MJ | 300,000,000,000,000 erg | 
| 40 MJ | 400,000,000,000,000 erg | 
| 50 MJ | 500,000,000,000,000 erg | 
| 60 MJ | 600,000,000,000,000 erg | 
| 70 MJ | 700,000,000,000,000 erg | 
| 80 MJ | 800,000,000,000,000 erg | 
| 90 MJ | 900,000,000,000,000 erg | 
| 100 MJ | 1,000,000,000,000,000 erg | 
| 250 MJ | 2,500,000,000,000,000 erg | 
| 500 MJ | 5,000,000,000,000,000 erg | 
| 750 MJ | 7,500,000,000,000,000 erg | 
| 1000 MJ | 10,000,000,000,000,000 erg | 
| 10000 MJ | 100,000,000,000,000,000 erg | 
| 100000 MJ | 1,000,000,000,000,000,000 erg |