Tech Tools — Alpine E & I

E&I Field Calculators

Quick reference calculators for electrical, instrumentation, controls, pipe flow, and industrial field-service work.

Pipe Flow 4-20 mA Ohm’s Law Voltage Drop Conduit Fill Metric Prefix

GPM to FPS / Pipe Velocity Calculator

Formula: Velocity ft/s = 0.4085 × GPM ÷ inside diameter²

Flow Rate, GPM Pipe Inside Diameter, inches

Velocity —

Pipe Area —

4-20 mA Scaling Calculator

Enter the mA signal, low range value, and high range value.

Input Signal, mA Low Range Value, value at 4 mA High Range Value, value at 20 mA Engineering Unit

Scaled Process Value —

Percent of Span —

Ohm’s Law Calculator

Enter voltage and current to calculate watts and resistance.

Voltage, V Current, A

Power —

Resistance —

Voltage Drop Calculator

Basic single-phase/DC voltage drop estimate using conductor resistance per 1000 ft.

Voltage Current, Amps One-Way Length, Feet Conductor Resistance, ohms per 1000 ft

Voltage Drop —

Voltage Drop Percentage —

Basic Conduit Fill Percentage Calculator

Use actual conduit internal area and conductor area from approved tables or manufacturer data.

Conduit Internal Area, square inches Area of One Conductor, square inches Number of Conductors Target Maximum Fill, %

Total Conductor Area —

Calculated Fill —

Target Comparison —

Metric Prefix Converter

Convert between pico, nano, micro, milli, base units, kilo, mega, and giga.

Value From Prefix To Prefix Unit Label, optional

Converted Value —

Base Unit Value —

These calculators are provided for general field reference only. Verify all calculations using applicable codes, project specifications, manufacturer documentation, engineering requirements, and approved installation standards.

Motor Cable Ampacity & Overload Calculator

Estimate motor branch-circuit conductor ampacity, suggested conductor size using the 75°C ampacity column, and motor overload protection settings.

Conductor Sizing Overload Protection Field Notes

Motor Conductor Sizing

For conductor sizing, use the applicable NEC motor FLC table value and multiply by 125%. This is separate from overload protection. Motor conductor sizing is generally based on the NEC motor FLC value, not necessarily the motor nameplate FLA.

Motor FLC for Conductor Sizing, Amps Conductor Material Adjustment Factor, if applicable Custom Adjustment Factor

Minimum Required Conductor Ampacity —

Suggested Minimum Conductor Size, 75°C Column —

Adjusted Conductor Ampacity —

Motor Overload Protection

For overload protection, use the motor nameplate FLA. Motors with a service factor of 1.15 or greater, or a temperature rise of 40°C or less, are commonly sized at 125% of nameplate FLA. Other motors are commonly sized at 115% of nameplate FLA.

Motor Nameplate FLA, Amps Motor Condition

Maximum Overload Setting —

Overload Percentage Used —

Field Notes

Do not confuse motor conductor sizing, motor overload protection, and breaker or fuse sizing. They are related but separate calculations.

Motor conductor sizing: commonly based on applicable NEC motor FLC × 125%.
Motor overload sizing: commonly based on motor nameplate FLA × 115% or 125%.
Service factor note: if service factor is 1.15 or greater, or temperature rise is 40°C or less, overload sizing commonly uses 125% of nameplate FLA.
Other motors: commonly use 115% of nameplate FLA for overload sizing.
Breaker/fuse sizing: short-circuit and ground-fault protection is a separate motor calculation.
75°C column: this calculator uses common 75°C ampacity values for copper and aluminum conductors.
Adjustment factors: use the correct adjustment/correction factors for the actual installation conditions.

Important: This calculator is for general field reference only. Verify motor conductor sizing, overload protection, short-circuit and ground-fault protection, temperature correction, adjustment factors, terminal ratings, local amendments, AHJ requirements, and project specifications using the currently adopted NEC and approved documentation.