Ohms on a dual coil is like water pressure on a garden hose. You will get all the pressure (resistance) on the single hose, but when you connect two hoses to the same water spicket the water pressure (resistance) is cut in half. IE: two 1.0 ohm coils is gonna be .5 ohms at the connector. Four 1.0 ohm coils will be .25 ohms. Ideally you want the coils to be the same to achieve even heating. If you don't have the Ohm's Law app for your phone, download it asap. When you use that app, you can put in any two variables and it will calculate the other two. A full 18650 battery is 4.2v so that's where you start, then put in the ohms and it will tell you your amps and watts. Amps is gonna be the power draining from your battery, and every battery has a different max discharge rating measured in amps. DO NOT EXCEED THAT RATING. Catastrophic failure with a lithium ion battery is detonation. There are video's on youtube if you wanna know how serious the detonation is, but trust me its not pretty... The other variable, wattage, is divided evenly to each of the coils. If a dual coil setup has 30 watts going to it, and the coils are the same, then each coil is getting 15 watts. Just let us know what you are trying to achieve and we will help you the best we can. Lets start with your setup. What mod and RBA's are you working with?