Ohm’ Law Formulas:
- Volts = Amperes X Ohms
- Amperes = Volts/Ohms
- Ohms = Volts/Amperes
- Watts = Volts X Amperes
- Watts = (Volts X Volts) / Ohms
- Watts = Amperes X Amperes X Ohms
- Ohms = Watts / (Amperes X Amperes)
Please see the various tables referred to in this section at:
Nichrome Technical Data Page
Note the amperage values in the Current/Temperature Table in the “Nichrome and Resistance wires” menu item above. As a general rule you can expect that the amperage value for a *coiled* wire is roughly 30-60% less than the capacity of a *straight* wire as referred to in the table. For *coiled* wire elements see “Nichrome Wire Tech Tips” PDF file. (accessible in scroll down menu above in “Nichrome and Resistance Wires.”)
Using Ohm’s Law above, & tables (see the Increased Resistance Table), you can calculate the watts at your intended voltage (115 being most common).
See the Wattage/Amperage/Hot Ohms Table. Note that it is based on 115 V.
Taking into account the available space, you can select a wire size that will provide the required wattage. From the amount of total Hot Ohms of your element design, you can use Ohms/Ft Table to estimate the amount of feet you will need of a given size.