81 standards-based electrical engineering tools, organized into 10 categories. Jump to a category or scroll through all of them below.
IDMT relay coordination and grading, differential and earth-fault protection, arc flash, breaker/fuse sizing, and generator paralleling/fault contribution.
IEC 60255 & IEEE C37.112 inverse-time curves. Add any number of relays to a chain and check full-range grading margin at every step.
Open calculator โEarth-fault IDMT trip time and optional instantaneous stage, reusing the verified IEC 60255-151 / IEEE C37.112 curve engine. Fully free โ no subscriber gate.
Open calculator โPercentage-bias dual-slope restraint characteristic trip/no-trip check, IEEE C37.91-consistent. Fully free โ no subscriber gate.
Open calculator โAvailable fault current at successive points down a radial network using the classic Base kVA Method. Fully free โ no subscriber gate.
Open calculator โIncident energy, arc flash boundary and PPE category โ IEEE 1584-2002 and Ralph Lee free, IEEE 1584-2018 as a subscriber feature.
Open calculator โGeneral continuous/non-continuous load OCPD sizing (NEC 210.19/215.2 + 240.4, or IEC 60364-4-43) and motor starting-current withstand sizing (NEC 430.52). Fully free โ no subscriber gate.
Open calculator โVoltage, frequency and phase-angle synchronization check (ANSI device 25 style) before closing a generator paralleling breaker. Fully free โ no subscriber gate.
Open calculator โPer-generator and total fault current contribution at a common bus, subtransient-reactance method. Fully free โ no subscriber gate.
Open calculator โLocation-based lookup of NEC 210.12(A) AFCI and 210.8(A) GFCI dwelling-unit protection requirements, with citations. Fully free โ no subscriber gate.
Open calculator โProspective and peak fault current from transformer kVA/%Z, with OCPD AIC and equipment SCCR adequacy check per NEC 110.9/110.10. Fully free โ no subscriber gate.
Open calculator โSPD Type recommendation by location, minimum MCOV from system voltage/grounding, and SCCR check against available fault current. Fully free โ no subscriber gate.
Open calculator โCable and conductor sizing, fill and pulling calculations, and overhead/distribution line voltage regulation and losses.
IEC 60364-5-52 current-carrying capacity and voltage drop, with derating, short-circuit withstand, CPC sizing and lifecycle cost as subscriber features.
Open calculator โIEC 60287 first-principles thermal-circuit current rating for single-core MV/HV cables, cross-checked against CIGRE TB880. Fully free โ no subscriber gate.
Open calculator โNEC Chapter 9 Table 1/4/5 (US) or IEC/BS 7671 45%/40% space-factor method (International). Fully free โ no subscriber gate.
Open calculator โNEC ยง392.22 width/area rules by tray type & cable category, or IEC 61537-style area-fill. Entirely a subscriber feature.
Open calculator โIEEE 1185 tension/capstan equations, sidewall bearing pressure & jam ratio. Entirely a subscriber feature.
Open calculator โHART/4-20mA capacitance-limited maximum cable length, minimum conductor size guidance, and general EMI separation-distance practice. Fully free โ no subscriber gate.
Open calculator โVoltage drop and regulation from your own conductor R/X per km, current, PF and length. Fully free โ no subscriber gate.
Open calculator โAnnual IยฒR energy loss estimate from peak load, diversity and load factor, using the loss-factor approximation. Fully free โ no subscriber gate.
Open calculator โFull NEC Article 310 four-step derating chain โ Table 310.16 base ampacity, ambient correction, bundling adjustment, and 110.14(C) termination cap. Auto-size or check a selected conductor. Fully free โ no subscriber gate.
Open calculator โ10-ft, 25-ft and outside unlimited-length feeder tap compliance checks against length, ampacity ratio, protection and terminal OCPD conditions. Fully free โ no subscriber gate.
Open calculator โSimplified Neher-McGrath / IEC 60287 equal-area equivalent-cylinder external thermal resistance โ bank-to-ambient temperature rise or maximum permissible losses. Fully free โ no subscriber gate.
Open calculator โOpen-area (perforation) ratio of a cable tray from width, length and open area, with LOW-HIGH grading. Fully free โ no subscriber gate.
Open calculator โEarthing grid design, lightning protection and rolling sphere method, touch voltage, and static/ESD hazard checks.
IEEE 80 grid resistance, GPR and tolerable touch/step limits, plus BS 7430 electrode sizing. Mesh/step voltage pass-fail, layered soil and parallel electrodes are subscriber features.
Open calculator โIEC 62305-1/2 risk assessment โ collection area, structure risk and minimum LPS class. Connected-line risk and SPD/LEMP protection sizing are subscriber features.
Open calculator โSingle air-terminal protection radius against the IEC 62305 rolling sphere for a given LPS class. Fully free โ no subscriber gate.
Open calculator โGround potential rise and touch voltage from an unbalanced neutral/earth current, checked against IEC 60364-4-41 limits. Fully free โ no subscriber gate.
Open calculator โHazardous-area bonding/grounding resistance check against the NFPA 77 static-electricity dissipation threshold. Fully free โ no subscriber gate.
Open calculator โCapacitive discharge spark energy (E=ยฝCVยฒ) vs. atmosphere Minimum Ignition Energy, per IEC 60079-32-1 screening practice. Fully free โ no subscriber gate.
Open calculator โBS 7430 single-rod resistance-to-earth from soil resistivity and rod geometry, graded against the common 25ฮฉ NEC 250.53(A)(2) practical threshold. Fully free โ no subscriber gate.
Open calculator โBS 7430 single-ring resistance-to-earth from soil resistivity, ring diameter and burial depth. Fully free โ no subscriber gate.
Open calculator โTransformer, CT, VT and busbar sizing/rating, plus insulation resistance and polarization index condition tests.
IEC 61869-2 CT ratio, itemized burden and ALF/knee-point voltage check. Saturation analysis, metering class, thermal/mechanical withstand and multi-ratio taps are subscriber features.
Open calculator โIEC 61869-3 voltage transformer ratio, voltage factor by earthing system, and burden vs. standard rated outputs. Protection class, thermal limiting output and open-delta residual voltage are subscriber features.
Open calculator โSizes a new transformer (or N-1 redundant group) from connected load, growth/safety margins, ambient derating, and standard ANSI/IEEE kVA ratings. Fully free โ no subscriber gate.
Open calculator โGenset sizing for running + motor-starting load, and transformer loss/efficiency/regulation from test data. NGR/NET earthing resistor sizing is a subscriber feature.
Open calculator โFirst-principles continuous ampacity and temperature rise for rectangular busbars. Short-time thermal withstand and electrodynamic force check are subscriber features.
Open calculator โIEEE 43 kV+1 minimum-IR check with 40ยฐC temperature correction. Fully free โ no subscriber gate.
Open calculator โPI = IR(10min)/IR(1min) with IEEE 43 condition bands and minimum-PI check by insulation class. Fully free โ no subscriber gate.
Open calculator โPower factor correction, harmonics, demand studies, voltage/load balance, unit conversion and tariff estimation.
IEC 60831 capacitor bank sizing with current/kVA reduction. Harmonic resonance, detuning reactor sizing and energy-savings analysis are subscriber features.
Open calculator โIEEE 519-2014 Table 1 (voltage) & Table 2 (current, TDD-referenced) distortion limit checks. Full per-order breakdown table and K-factor estimate are subscriber features.
Open calculator โLoad-category demand-factor method with design current and breaker sizing. Multi-board site aggregation & transformer sizing is a subscriber feature.
Open calculator โNEMA-style % voltage unbalance and motor derating factor from the NEMA MG1 / ANSI C84.1 curve. Fully free โ no subscriber gate.
Open calculator โPer-phase load balance and neutral current from the standard 3-phase phasor formula. Fully free โ no subscriber gate.
Open calculator โSingle-phase and three-phase power-triangle and current conversions from a load profile (voltage, power factor, and any one known quantity). Fully free โ no subscriber gate.
Open calculator โEstimates a monthly electricity bill from itemized time-of-use energy, peak demand charge, fixed charge and an optional power-factor penalty. Fully free โ no subscriber gate.
Open calculator โDiversity factor and coincident maximum demand for a group of loads on a shared feeder, transformer or panel, with compute and solve-for-unknown modes. Fully free โ no subscriber gate.
Open calculator โSingle-family dwelling service load via NEC Art. 220 Standard Method or 220.82 Optional Method, with recommended minimum service size. Fully free โ no subscriber gate.
Open calculator โMotor branch-circuit sizing, motor protection, and VFD energy savings.
NEC Article 430 (FLC tables, branch-circuit/OCPD/overload/disconnect sizing) or IEC general method, plus starting-method voltage-dip check. Entirely a subscriber feature.
Open calculator โOverload relay setting & trip class (NEC 430.32 / IEC 60947-4-1), AC-3/AC-4 contactor sizing, and ground-fault pickup guidance by system grounding type. Fully free โ no subscriber gate.
Open calculator โAffinity-law (power โ speedยณ) energy and cost savings estimate for switching a centrifugal pump/fan from throttled to VFD control. Fully free โ no subscriber gate.
Open calculator โSteady-state motor shaft torque from output power and operating speed, in Nยทm or lb-ft. Fully free โ no subscriber gate.
Open calculator โTime to accelerate a motor-load system from standstill to rated speed, from total inertia and average net accelerating torque. Fully free โ no subscriber gate.
Open calculator โScreens a candidate soft starter's rated current against motor FLA with temperature/altitude/duty derating, plus voltage check. Fully free โ no subscriber gate.
Open calculator โMotor nameplate vs VFD rating compatibility screen โ voltage match, current loading, base V/Hz ratio, synchronous speed, slip. Fully free โ no subscriber gate.
Open calculator โBattery sizing, UPS sizing, emergency power sequencing, genset fuel, and energy storage (BESS).
IEEE 485 duty-cycle section method for lead-acid battery capacity. Random loads, cell/voltage window checks and charger sizing are subscriber features.
Open calculator โRequired UPS kVA rating from critical load, margin and redundancy configuration, plus approximate battery energy/Ah for the stated backup time. Fully free โ no subscriber gate.
Open calculator โNFPA 110 Type/Class classification, UPS-to-genset bridge timing check, and staged load-step pickup planner. Entirely a subscriber feature.
Open calculator โRuntime and hourly cost from tank size and your genset's own fuel consumption rate. Fully free โ no subscriber gate.
Open calculator โIEEE 1547 / IEC 62933 usable-energy, nameplate capacity, C-rate and PCS voltage-window sizing with AC cable sizing. Multi-bank site aggregation & cycle-life estimate are subscriber features.
Open calculator โNEC Art. 700/701/702 automatic/manual transfer switch ampacity from connected load, 125% continuous-load factor, next standard UL 1008 rating. Fully free โ no subscriber gate.
Open calculator โCheck emergency lighting battery runtime against the 90-minute NFPA 101 / NEC 700.12 minimum, or size required Wh and Ah capacity with aging, DoD and inverter efficiency. Fully free โ no subscriber gate.
Open calculator โPreliminary CHP electrical capacity from electrical and thermal baseload demand and heat-to-power ratio, sized to the more limiting baseload. Fully free โ no subscriber gate.
Open calculator โSimplified 0-100 Stability Index for islanded microgrid screening from generation headroom, inertia and reserve margin. Fully free โ no subscriber gate.
Open calculator โBESS power/energy sizing to shave peak demand to a target level, with demand-charge savings and simple payback. Fully free โ no subscriber gate.
Open calculator โ4-20mA loop budgets, intrinsic safety, thermocouple/RTD conversion, and fire & gas loop power.
Loop voltage budget for a 2-wire loop-powered transmitter โ wire voltage drop, transmitter headroom, and maximum cable length by AWG. Fully free โ no subscriber gate.
Open calculator โIEC 60079-11 entity concept โ voltage/current/power and capacitance/inductance checks (with the 1% rule) for combining a barrier with IS field apparatus and cable. Fully free โ no subscriber gate.
Open calculator โNIST ITS-90 thermocouple mV-to-temperature with cold-junction compensation (K/J/T/E), plus IEC 60751 Callendar-Van Dusen RTD conversion with lead-wire compensation. Fully free โ no subscriber gate.
Open calculator โStandby and alarm-condition voltage budget for a multi-detector fire/gas initiating device circuit with an end-of-line resistor. Fully free โ no subscriber gate.
Open calculator โSolar PV string/inverter sizing and EV charge point sizing โ with room to grow as more renewables tools ship.
IEC 62548 & IEC 60364-7-712 string voltage window, inverter matching, and DC/AC cable sizing. Multi-string parallel arrays with combiner/feeder sizing are a subscriber feature.
Open calculator โIEC 61851-1 / 60364-7-722 / 62955 charge point cable, breaker and RCD sizing. Multi-point site demand with load-management diversity is a subscriber feature.
Open calculator โOff-grid PWM/MPPT charge controller current rating from array Isc or power/battery voltage, NEC 690.8(A) 125% factor. Fully free โ no subscriber gate.
Open calculator โRecommended fixed-mount PV tilt angle from site latitude โ year-round, two-season, summer- or winter-biased. Fully free โ no subscriber gate.
Open calculator โGrid-tied DC:AC ratio (ILR) sizing/grading, or off-grid continuous + surge inverter capacity from a connected load. Fully free โ no subscriber gate.
Open calculator โElectrical power output from rotor diameter, wind speed, air density, power coefficient (Cp) and generator efficiency. Fully free โ no subscriber gate.
Open calculator โHVAC electrical sizing, lighting design, elevators, data-center PUE, life-cycle cost, and heat management.
Motor-compressor branch-circuit sizing (NEC Art. 440) or IEC general method. Single motor free โ multi-motor combination-load & VFD-fed motor are subscriber features.
Open calculator โLumen method (EN 12464-1 or IES Handbook). Interior room types are free โ exterior/area lighting and EN 1838 emergency lighting checks are subscriber features.
Open calculator โTraction elevator motor power from load/speed/balance/efficiency, plus NEC Table 620.14 feeder demand factor for a group of elevators. Fully free โ no subscriber gate.
Open calculator โPower Usage Effectiveness (PUE) & DCiE from facility/IT energy, overhead cost, and a Green Grid efficiency-band classification. Fully free โ no subscriber gate.
Open calculator โDiscounted-cash-flow life-cycle cost comparison of two options (e.g. standard vs. premium efficiency) with present worth, equivalent annual cost and simple payback. Fully free โ no subscriber gate.
Open calculator โElectrical trace-heating power from pipe insulation heat loss, heater cable selection, and circuit voltage-drop/breaker sizing. Fully free โ no subscriber gate.
Open calculator โNatural-convection heat-dissipation check for panel/MCC enclosures, with IEC 60890-derived forced-air fan sizing if needed. Fully free โ no subscriber gate.
Open calculator โItems under active consideration for future batches. Not live, not linked โ listed here for visibility only.