Tools
Reference tables and tools for electricians and technicians
Short reference pages for the numbers you look up on the job. Every value is calculated from the formula the page states, not copied by hand, and the page says what the number is and what it is not. Each page also shows how to take the matching reading with a Bluetooth multimeter and the app.
iPhone and iPad (iOS 17 or later): free on the App Store. Android later.
All tools
AWG to mm2
AWG 0000 to 40 with diameter in mm, cross-section in mm2 and the resistance of solid copper, plus the nearest AWG for common metric sizes.
Resistor color code
Chart of the IEC 60062 resistor colour code for 4, 5 and 6 band resistors, three worked examples, which end to start from and how to confirm the value with ohms.
Multimeter symbols
Every symbol on a multimeter dial and display with a drawing and a one-line meaning, from the continuity symbol to CAT ratings and the COM, V-ohm, mA and 10 A jacks.
Ohm's law calculator
Enter any two of voltage, current, resistance and power and get the other two, with the formulas and three worked examples.
Parallel resistor calculator
Enter 2 to 6 resistor values and get the total in parallel and in series, with the formulas and three worked examples.
Voltage divider calculator
Enter Vin, R1 and R2 to get the output voltage, the current and the power in each resistor, or solve R2 for a wanted output, with the formulas and three worked examples.
Voltage drop calculator
Enter conductor material, size, one-way length, current and source voltage to get the voltage drop in volts and percent, with the formula, the assumptions and three worked examples.
PT100 table
Pt100 resistance in ohms from -200 to 850 °C in 5 °C steps, the IEC 60751 equation behind it, tolerance classes A and B, and how to read a sensor with a multimeter.
Type K table
Type K thermocouple voltage in millivolts from -200 to 1370 °C in 10 °C steps (reference junction 0 °C), the NIST ITS-90 source, and why a multimeter reading needs cold-junction compensation.
Battery checker
Pick a battery, type the voltage your multimeter shows and read the verdict with the next step. Free, in your browser, and nothing you type is sent anywhere.
What is here
The first page is the AWG to mm2 table: wire gauge 0000 to 40 with diameter, cross-section and the resistance of solid copper, plus the nearest AWG for common metric cable sizes. More tables and working calculators follow; each one gets its own page in this list. The battery checker works from a table rather than a formula: its voltage bands come from battery makers' datasheets, and the page names its sources.
Looking for step-by-step jobs instead of numbers? See the guides.
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