Tools
Calculators, drills, labs and printable sheets — 36 of them, sorted by what they are for. Every calculator works in imperial or metric (the switch at the top of the page), and any result can be kept: copy it, text it, share it, print it, or have the site email it to you. Where a number comes from the code — an ampacity, a fill limit, a derating factor — you type it from your own code book and the tool does the arithmetic.
Drills
- 1st year
Tape measure test
Read a tape to the nearest 1/16", timed or free practice.
- 1st year
Fraction / decimal drill
Fractions of an inch to decimals and back.
- 1st year
Ohm's law practice
Solve for V, I, R or P at three levels, marked on the spot.
- 1st year
Series / parallel practice
Totals, string current and voltage drops across resistors.
- 1st year
Conversion drill
Inches ↔ millimetres, feet ↔ metres.
- 2nd year
Offset math practice
Distance between bends from the rise and angle.
- 2nd year
Trade math practice
Mixed practice and a printable 20-question worksheet.
Formulas & sheets
- 1st year
Ohm's law & power wheel
Every rearrangement of V, I, R and P in one circle.
- 1st year
Fraction / decimal / mm chart
Sixteenths to decimals to millimetres, printable.
- 2nd year
Bending multipliers & shrink
Multiplier and shrink per angle, from the trigonometry.
- 3rd year
Single & three phase formulas
Power and current formulas on one page.
- 1st year
Trade math cheat sheet
Fractions, triangles, percent and area.
AC theory
- 2nd year
Capacitive & inductive reactance
XL and XC at any frequency, the impedance with a resistance in series, and the resonant frequency.
- 2nd year
RC / RL time constant
τ = RC or L/R, the five-time-constant table, and the percentage reached at any moment.
- 2nd year
Power triangle & power factor
Volts, amps and power factor, single- or three-phase: kVA, kW, kVAR and the angle, drawn to scale.
Basic circuits
- 1st year
Ohm’s law & power calculator
Type any two of volts, amps, ohms and watts; get the other two and the formula that did it.
- 1st year
Resistor colour code
Pick four or five bands and read the value, the tolerance and the range it may measure.
- 1st year
Series & parallel resistance
Up to eight resistors: the series total, the parallel total, and the current at a supply voltage.
Trade math
- 1st year
Efficiency & percent
Input and output power in watts, kilowatts or horsepower: efficiency, losses, or the input a load needs.
- 1st year
Wire length & area converter
Feet and metres, and conductor area between AWG, kcmil, circular mils and mm².
- 1st year
Battery runtime & bank size
Volts, amp-hours, depth of discharge and inverter efficiency: hours on a load, or the Ah a runtime needs.
Motor control
Power quality
- 4th year
Power factor correction calculator
kVAR needed to go from one power factor to another, the current it saves, and the capacitance per phase.
- 4th year
Voltage unbalance calculator
Percent unbalance from three line voltages or currents, by maximum deviation and by the negative-sequence method.
Three-phase
Transformers
Wiring
Drives
Instrumentation
Motors
Protection
Services
No tool matches that. Try the site search, which also looks through lessons and diagrams.
Related
- Learn by year — lessons for 1st to 4th year and journeymen
- Practice drills
- Printable formula sheets
- Motor control course
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