well... according to formula.. with 300% and no bonuses. Whatever you are wearing/carrying, you can't sneak to someone who has 10 Perception.. (20+3*10-300/6 = 0)
As i assume everyone as at least 8 Perception, sneak is almost impossible. Even if you have some bonuses, because of your armor and stuff you carry, result of the formula will be positive. Consequently, You need to be absolutely naked, carry nothing at least, have ~300% and use some bonus.
If your victim is too far from scenery objects like barrels, tables, walls, you can forget it. :x
Moreover this formula is static, no dice roll to let you/your victim some chance.