Engineering tools
Calculators and reference tables for the questions that come up when you meter, monitor and control energy: power and current, cables, CTs, sensor signals, Modbus and M-Bus.
Most used
Electrical power and current
Convert between power, current and voltage, and resolve the power triangle for single-phase and three-phase loads. Start here for most sizing and monitoring questions.
- kW to ampsConvert kW or kVA to amps, or amps to kW or kVA, for DC, single-phase and three-phase circuits.kW, V, PF → A
- Three-phase powerWork out active, reactive and apparent power for a balanced three-phase load from voltage, current and power factor.V, A, PF → kW
- kW, kVA, kvar and power factorFind the rest of the power triangle (kW, kVA, kvar and power factor) from two known values.Two of kW, kVA, kvar, PF → the rest
- Transformer currentWork out the full-load primary and secondary current of a transformer from its kVA rating and voltages.kVA, V → A
- Power factor correctionEstimate the kvar needed to raise a lagging power factor to a target, and the current it saves.kW, PF → kvar
- Voltage unbalanceCalculate voltage unbalance from three line-to-line readings using the NEMA method.3 × V → %
- THD and TDDCalculate voltage or current THD, or current TDD, from measured harmonic magnitudes.Harmonics → THD %
- Ohm’s lawFind volts, amps, ohms or watts from any two known values.Any two → V, A, Ω, W
- Motor full-load currentFind a motor’s full-load current from its kW or hp rating, efficiency and power factor.kW or hp, V → A
Cables and conductors
Estimate voltage drop, convert wire gauges and work out conductor resistance. Each result states the standard it follows and what it does not check.
Metering and CTs
Choose a current transformer that fits the conductor and the load, and check an existing CT against its burden.
Energy cost and demand
Turn metered energy and demand into a bill, a load factor or an interval demand figure you can check against a utility invoice.
- Appliance energySee what a fridge, heater or other appliance uses and costs each year.W, duty, hours → kWh and cost
- Electricity costEstimate an electricity bill with energy, demand and fixed charges shown separately.kWh, kW, rates → cost
- Interval demandTurn the energy recorded in one demand interval into average demand in kW.kWh, minutes → kW
- Load factorCheck how evenly a site uses its peak demand over a billing or reporting period.kWh, kW, hours → %
- kW to kWhConvert kW to kWh for a running time, or kWh back to average kW, with the cost of running.kW, h → kWh
- Energy monitoring payback calculatorEstimate the payback of an energy monitoring system from spend, expected saving and hardware cost.€, % → months
Energy units, gas and carbon
Convert between energy units, turn gas meter readings into kWh and put a carbon figure on the energy a site uses.
- Gas m³ to kWhConvert gas meter readings or volume to kWh using the calorific value and correction factor.m³, MJ/m³ → kWh
- Energy unit converterConvert kWh, MJ, Btu, therms and toe, or kW, Btu/h, tons and hp, with every unit at once.kWh ↔ MJ, Btu, therm
- Carbon emissions calculatorConvert kWh of electricity or gas to CO₂e with dated, sourced factors or your own.kWh → kg CO₂e
Sensors and signals
Scale 4-20 mA and 0-10 V signals to engineering values, check loop headroom and convert RTD resistance to temperature.
- 4-20 mA scalingScale a 4-20 mA signal to engineering units or back, including square-root flow.mA ↔ value
- 0-10 V signal scalingScale an analogue voltage signal to engineering units, including spans that do not start at zero.V ↔ value
- 4-20 mA loop voltageCheck a 4-20 mA loop has enough supply voltage at its design current.V, Ω → V headroom
- Pt100 and Pt1000Convert between resistance and temperature for Pt100 and Pt1000 sensors, with tolerance class limits.°C ↔ Ω
- RTD lead resistance errorEstimate the temperature error that lead resistance adds to a two-wire or three-wire RTD.Ω or m → °C
Enclosures and humidity
Read an IP rating before choosing where a device goes, and work out the dew point to see where condensation will form.
Modbus and serial
Translate register addresses, decode register values, check frames and plan RS-485 wiring before you commission a Modbus device.
- Modbus address converterWork out which register a device map means: zero-based offset, one-based number or 40001-style reference.40001 → 0x0000
- Modbus register decoderDecode integer and floating-point values from Modbus registers in each byte order.Hex → float, int
- Modbus function and exception codesLook up any public Modbus function code, data object or exception code, with its request limits.83 02 → meaning
- Modbus CRC and LRCCalculate the CRC-16 for a Modbus RTU frame and see the byte order on the wire.Frame → CRC or LRC
- Modbus RTU timingCalculate character and frame timing on a Modbus RTU link, and how long a polling cycle takes.Baud, bytes → ms
- RS-485 termination and biasCheck where termination and bias resistors belong on an RS-485 Modbus network.Wiring → checks
- IEEE 754 float converterConvert decimal numbers to IEEE 754 hex and back, with the Modbus register words in every byte order.Decimal ↔ hex
M-Bus and pulse
Scale pulse outputs, plan counter rollover and budget a wired M-Bus segment and its addresses.
- Pulse meter scalingConvert pulse counts to energy and check pulse rate, pulse width and counter capacity.Pulses, imp/kWh → kWh, Hz
- Wired M-Bus segmentCheck unit loads, far-end voltage and bus capacitance for a wired M-Bus segment.Meters, cable → checks
- M-Bus address plannerCheck an M-Bus primary address schedule for duplicates and reserved addresses before commissioning.Addresses → checks
Wireless links and radio power
Convert radio power and account for gains and losses before checking a wireless link on site.
HVAC, thermal and process
Check heat meters, chillers, heat pumps, compressors, pumps and generators against the measurements you already have.
- Heat meter checkEstimate heat output from flow and temperature difference to check a heat meter reading.m³/h, ΔT → kW
- Chiller COPCalculate chiller COP, kW/ton and EER from cooling output and electrical input.kW, tons → COP
- Heat pump COPCalculate a heat pump's instantaneous COP or measured-period performance factor from heat delivered and electricity used.kWh heat, kWh in → COP
- Compressed air specific powerCalculate compressed air specific power: electrical input per unit of delivered air flow.kW, m³/min → kW/(m³/min)
- Pump affinity lawsEstimate how flow, head and power change when a centrifugal pump's speed changes.rpm → flow, head, kW
- Generator fuel consumptionCalculate generator fuel use per hour and per kWh, and the average load over a run.L, kWh → L/kWh
Solar, storage and flexibility
Estimate solar generation and battery runtime, size EV charging within site headroom, and measure demand response delivery.
- Solar PV generationModel monthly solar generation from historical weather and your array layout.Location, kWp, tilt → monthly kWh
- Battery runtimeCalculate energy above reserve and runtime, with discharge losses and the inverter power limit.kWh, SOC, efficiency, kW → runtime
- EV charging capacitySee how many EV chargers a site can run at once, interval by interval, within its import limit.kW series → chargers
- Demand response eventMeasure the reduction delivered in a demand response event, any shortfall, and the rebound afterwards.kW series → kWh
No tool matches that search. Try a quantity such as “amps”, a protocol such as “Modbus”, or a device such as “CT”.
How these tools work
Each tool shows its result as you type, with the formula written out using your own numbers, so you can check the working rather than trust a number. The method, its limits and the standards or manufacturer documents it follows are listed under every calculator.
The tools are free and need no account. A link copied from a tool opens with the same values and the same result, which makes it easy to share a calculation with a colleague or keep it with a design. Results are engineering estimates for planning and commissioning, not a substitute for the equipment documentation or your local wiring rules.