Calculators
35 calculators for the arithmetic that comes up on real jobs. Every one shows its work, names the table value it used, and states what it does not account for, so a qualified person can check it rather than trust it.
Electrical
Conductor Ampacity with DeratingAllowable ampacity after ambient temperature correction and the adjustment for more than three current-carrying conductors, with the small-conductor overcurrent limit applied.Conduit Fill CalculatorPercentage fill for a conduit run from conductor count and size, checked against the 40, 31, and 53 percent limits, with the smallest conduit that fits.Ohm's Law and Power CalculatorSolve voltage, current, resistance, and power from any two known values, with the relationships used shown.Three-Phase Power CalculatorApparent, real, and reactive power from line voltage, line current, and power factor, or the current a given load will draw.Voltage Drop CalculatorVoltage drop over a conductor run, by wire size, material, distance, and load, using the circular-mil method. Shows the arithmetic so it can be checked.Wire Size Calculator for Voltage DropThe smallest conductor that keeps voltage drop within a chosen limit for a given load, distance, and system voltage, with the required circular mils shown.
Control Panels
Control Panel Heat Load and Temperature RiseInternal temperature rise for a control enclosure from component heat, solar gain, and enclosure surface area, with the cooling shortfall if any.DC Power Supply Load BudgetTotal 24 VDC load from controller, I/O, transmitters, relays, and network gear, with headroom applied and the heat the supply adds to the enclosure.Motor Branch Circuit SizingConductor, overload, short-circuit protection, and disconnect sizing for a three-phase motor branch circuit, from the code full-load current rather than the nameplate.Transformer Sizing and Full-Load CurrentPrimary and secondary full-load current for a transformer, plus the approximate available fault current at the secondary from the impedance.UPS and Battery RuntimeHow long a battery will carry a control load, from capacity, voltage, depth of discharge, and inverter efficiency.
Instrumentation
4-20 mA Loop Resistance BudgetMaximum loop resistance a two-wire transmitter can drive from a given supply voltage, and whether the loop you have described has enough headroom.4-20 mA Scaling CalculatorConvert between milliamps, percent of span, and engineering units for a 4-20 mA loop, in either direction, with NAMUR fault thresholds shown.Analog Input ResolutionResolution in engineering units per count for an analog input, from converter bit depth and calibrated range, with the smallest meaningful change.Analog Raw Counts to Engineering UnitsConvert between the raw integer an analog input card reports and the engineering value, in either direction, with the resolution per count.Differential Pressure Flow and Square Root ExtractionFlow from a differential pressure signal with square root extraction, including the low-flow cutoff and the resolution penalty near zero.RTD Resistance and TemperatureConvert between platinum RTD resistance and temperature using the IEC 60751 Callendar-Van Dusen relationship, with lead resistance error shown.
PLC & Data
Data Size ConverterConvert between bytes, kilobytes, megabytes, and gigabytes in both the decimal and binary conventions, which differ by a growing margin.Historian Storage SizingStorage a process historian will consume from tag count, sample rate, retention, and compression, with the daily and annual growth.IEEE 754 Floating Point InspectorConvert between a floating point value and its raw 32-bit representation, showing sign, exponent, mantissa, and the two Modbus registers in either word order.Modbus Register Address ConverterConvert between the traditional data model number such as 40001 and the protocol address that actually goes on the wire, with the function code shown.Modbus Serial Poll TimeHow long a Modbus RTU transaction takes at a given baud rate, and how many devices a serial bus can poll within a required update period.Number Base and Bit ConverterConvert between decimal, hexadecimal, binary, and octal, with the bit pattern shown and the two-complement signed interpretation for 16 and 32 bit words.PLC Data Type RangesValue ranges for the IEC 61131-3 data types, with a check of whether a value fits and what it will do if it does not.
Networking
Fiber Optic Loss BudgetOptical loss across a fiber link from length, connectors, and splices, compared against the transceiver budget with the margin remaining.IP Subnet CalculatorNetwork address, broadcast, usable host range, and host count for an IPv4 address and prefix, with the notes that matter on a control network.SCADA Polling BandwidthBandwidth a polling scheme consumes across a set of remote sites, and whether the communication path can carry it.
Water & Wastewater
Chemical Dosing CalculatorChemical feed rate from dose and flow, in pounds per day and in gallons per day of solution, with the metering pump setting.Detention Time CalculatorHow long water stays in a tank or basin at a given flow, in hours and minutes, with the volume turnover per day.Pipe Velocity and Friction LossVelocity and Hazen-Williams friction loss for a water pipe, with the head loss over the run and the velocity checked against practical limits.Pump Affinity LawsHow flow, head, and power change with pump speed or impeller diameter, and the energy saving a variable frequency drive can deliver.Pump Horsepower and Total Dynamic HeadHydraulic horsepower, brake horsepower, and motor input power from flow, head, specific gravity, and efficiency.Tank and Basin VolumeVolume of a cylindrical or rectangular tank at a given level, in gallons, cubic feet, and cubic metres, with the volume per foot of depth.Wet Well Volume and Pump Cycle TimeWorking volume, fill time, pump-down time, cycle length, and starts per hour for a wet well, including the worst-case inflow for cycling.
Conversions
Reference tables
The lookup tables behind several of these calculators, published separately so the values can be read directly.
- Conductor Ampacity TableAllowable ampacity for copper and aluminum conductors at the 60, 75, and 90 degree C columns, for not more than three current-carrying conductors at 30 degrees C ambient.
- Ambient Temperature Correction FactorsMultipliers applied to conductor ampacity when the ambient temperature differs from 30 degrees C, by insulation temperature rating.
- Adjustment Factors for Conductor CountAmpacity multipliers applied when more than three current-carrying conductors share a raceway or cable.
- Wire Gauge, Circular Mils, and AreaCircular mil area and approximate insulated cross-sectional area for AWG and kcmil conductor sizes.
- Three-Phase Motor Full-Load CurrentFull-load current for three-phase induction motors by horsepower and voltage, used for sizing conductors and overcurrent devices.
- Standard Overcurrent Device RatingsThe standard ampere ratings for fuses and inverse-time circuit breakers, used when rounding a calculated value to an available device.
- EMT Conduit Areas and Fill LimitsInternal area of electrical metallic tubing by trade size, with the usable area at the 53, 31, and 40 percent fill limits.
- PLC Data Type RangesBit width and value range for the IEC 61131-3 elementary data types, with the practical notes that matter in controller programming.
- 4-20 mA Signal ReferenceCurrent, percent of span, and voltage across a 250 ohm input for a 4-20 mA loop, including the NAMUR fault thresholds.
- Enclosure Type RatingsWhat each enclosure type rating protects against, and where each is normally used in controls work.
- Controls Unit Conversion ReferenceThe conversions that come up constantly in controls and water work: pressure, flow, level, power, and temperature.
Direct contact
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Content on this site is general technical reference information. It is not engineering advice for a specific installation. Always follow the applicable codes, standards, manufacturer documentation, and your own site safety procedures. Verify against the equipment in front of you before you act.