Free tools
Engineering Calculators
Quick screening checks built by our licensed Professional Engineers. Each tool answers one question from a few numbers you already have, using a published method such as NEC Chapter 9 or IEEE 1584-2018.
The result is a screening estimate, not a study. The tools cannot see your equipment, settings or site, so treat the answer as a first look. Designs, equipment ratings and arc flash labels need a study by a licensed engineer.
Which tool do I need?
Pick the question closest to yours.
Electrical power
Circuits, panels, conduit and the equipment that feeds them.
Voltage drop calculator NEC Chapter 9
Is my wire big enough for this run?
Gives the percent drop and the voltage left at the load, and suggests a larger wire when the run is over the limit.
For
- Homeowner
- Electrician
- Engineer
Have on hand
- Voltage and current of the circuit
- Wire size and material
- One-way length of the run
Wire size calculator NEC 310.16
What size wire does this load need?
Gives the smallest copper or aluminum conductor after the terminal, ambient and bundling checks, the breaker or fuse size, and a link to check voltage drop.
For
- Homeowner
- Electrician
- Engineer
Have on hand
- Load current, and whether it runs 3 hours or more
- Wire insulation and the terminal rating
- Ambient temperature and wires in the raceway
Available fault current calculator Point-to-point
Can my panel handle the available fault current?
Estimates the fault current at the transformer and at your equipment, then compares it with the breaker or panel rating.
For
- Electrician
- Facility manager
- Engineer
Have on hand
- Transformer kVA, voltage and %Z from the nameplate
- Length, size and material of each cable run
- Interrupting rating (AIC) of the breaker or panel
Arc flash calculator IEEE 1584-2018
How much arc flash energy is at this equipment?
Estimates the incident energy at the working distance and the arc flash boundary. It does not choose PPE or make a label.
For
- Facility manager
- Electrician
- Engineer
Have on hand
- System voltage and equipment type
- Bolted fault current at the equipment
- Clearing time of the upstream protective device
Conduit fill calculator NEC Chapter 9
Will these wires fit in this conduit?
Adds up the conductor areas and checks them against the NEC fill limit, with the next trade size when they do not fit.
For
- Electrician
- Engineer
Have on hand
- Raceway type and trade size
- Number, size and insulation of the conductors
Transformer calculator kVA and full-load amps
What size transformer, and what current?
Converts kVA to primary and secondary full-load current, or a load in amps or kW to the next standard kVA rating.
For
- Electrician
- Facility manager
- Engineer
Have on hand
- Single-phase or three-phase
- Primary and secondary voltages
- The kVA rating, or the load in amps or kW
Motor circuit calculator NEC Article 430
What wire, breaker and overload for this motor?
Gives the table full-load current, the conductor size at 125%, the overload setting and the largest breaker or fuse under Table 430.52.
For
- Electrician
- Engineer
Have on hand
- Motor horsepower, voltage and phase
- Nameplate current and service factor
- The breaker or fuse type
4-20 mA loop calculator NAMUR NE 43
What does this 4‑20 mA reading mean?
Converts between loop current and the process value, and checks that the loop has enough voltage at full scale.
For
- Electrician
- Engineer
Have on hand
- Calibrated range of the transmitter
- Loop current or process value
- Supply voltage, resistor and cable length for the voltage check
Not sure which check you need?
Tell us what you are trying to decide. An engineer will point you to the right tool, or tell you when a study is the better answer.
Ask an engineer
Corrosion and CP
Metals in contact, and structures in soil or water.
Galvanic corrosion chart Anodic index
Will these two metals corrode each other?
Shows which metal corrodes, how serious the pairing is where the joint sits, and practical ways to reduce the attack.
For
- Homeowner
- Facility manager
- Engineer
Have on hand
- The two metals
- Where the joint is: indoors, outdoors or buried
- Which of the two parts is smaller
Cathodic protection calculator Current and anode life
How much CP current, and how long will the anodes last?
Estimates the current a coated or bare steel structure needs and how long magnesium, zinc or aluminum anodes last, with every typical value editable.
For
- Engineer
- Pipeline operator
- Facility manager
Have on hand
- Pipe size and length, or the surface area
- Coating condition and soil or water
- Anode material, size and number
Learn and explore
A circuit simulator and interactive explainers that show the methods behind our studies.
Circuit simulator Runs in your browser
How does this circuit behave?
Draw a circuit with resistors, capacitors, inductors and sources, then read every voltage and current, with guided lessons.
For
- Student
- Engineer
Have on hand
- A circuit to try, or one of the built-in examples
Interactive explainers
- Read a CP test stationOn, instant-off and IR drop at a test station, with an interrupter you can adjust.Cathodic Protection Potential Surveys
- Walk through a sample arc flash studySelect a bus to see its label, the inputs behind it and the device that clears the arc.Arc Flash Studies
- Plot Wenner soil resistivity readingsEnter four-pin readings from two traverses and see a two-layer screening fit.Soil Corrosivity Analysis
- Build a data request for a power studyA printable checklist of the system data an arc flash, short circuit or coordination study needs.Arc Flash Studies
- How a Ufer ground worksA step-by-step drawing of a concrete-encased electrode in a building footing.Article
- Fall of potential: probe spacing and the plateauMove the current probe and see why the reading levels off only when the probes are far enough apart.Article
Need more than a screening estimate?
A study starts from your one-line diagram, nameplates and field readings, and a licensed PE seals it where required.