In any hedge, you should make sure you are not naked. Some responses given above lead to naked positions. Do not do it. Positive theta means you sell premium. Negative requires you earn premium. Here is an example. Sell a strandle. Theta is positive (and maximum). Calculate theta. You should have in any model/software. Call this Theta1. Buy a number of strangles. Calculate theta. Call it Theta2. Theta2 is negative. So at the start, if you want to be theta neutral, for each straddle you sell, but -(Theta1/Theta2). The minus is becuase Theta2 is negative. Since Theta1 is greater than Theta2, the number of strangles if higher than the number of straddles. If you should less than this number, you are overall theta postive. If you choose more, you are overall theta negative. Note that you must have at least one strangle for each straddle, otherwise you are naked. Remark: this hedge changes since theta is dynamic and varies with changes in other variables. So you need to make changes if you want to be neutral. I use a straddle and two strangle for this situation. When undelying does not move, I earn theta (because of straddle). When the underlying moves far away, the strangle kicks in and the whole position becomes eirther one call or one put.