Ohm's law Voltage
V = I * R
The basic starting point for quick voltage and resistance checks.
- V = voltage
- I = current
- R = resistance
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Electrical Formula Finder
Search a browser-local sheet of recurring electrical formulas so engineers can get to the right relation faster than digging through old notes or reference tabs.
Electrical-only lookup
Results13 formulas matched
Single-phase power Power
P = V * I * pf
Useful for current and load conversions in single-phase circuits.
- P = real power
- V = voltage
- I = current
- pf = power factor
Three-phase power Three-phase
P = sqrt(3) * V * I * pf
A common relation for balanced three-phase loads and supply sizing.
- P = real power
- V = line voltage
- I = line current
- pf = power factor
Current from power Load
I = P / (V * pf)
Helpful when a load is known in watts or kilowatts but current is needed.
- I = current
- P = power
- V = voltage
- pf = power factor
Single-phase voltage drop Voltage
Vd = 2 * I * R * L / 1000
A quick estimate for single-phase or DC style line runs.
- Vd = voltage drop
- I = current
- R = resistance in ohm/km
- L = one-way length in meters
Three-phase voltage drop Voltage
Vd = sqrt(3) * I * R * L / 1000
A quick estimate for balanced three-phase line runs.
- Vd = voltage drop
- I = current
- R = resistance in ohm/km
- L = one-way length in meters
Voltage drop percent Voltage
%Vd = (Vd / V) * 100
Useful when comparing a line drop against a project limit.
- Vd = voltage drop
- V = nominal system voltage
Conduit fill percent Fill
fill % = total cable area / conduit area * 100
A practical browser-local shortcut for quick routing checks.
- total cable area = sum of cable effective areas
- conduit area = available conduit area
Breaker margin Protection
margin = breaker rating - design current
A fast way to see whether the chosen breaker is comfortably above the expected current.
- margin = available current margin
- breaker rating = protective device rating
- design current = calculated load current
Single-phase apparent power Load
kVA = V * I / 1000
Useful for quick transformer and feeder checks.
- kVA = apparent power
- V = voltage
- I = current
Three-phase apparent power Three-phase
kVA = sqrt(3) * V * I / 1000
A common feeder and transformer lookup relation.
- kVA = apparent power
- V = line voltage
- I = line current
Lighting load from density Lighting
P = area * load density
Useful for quick planning and early layout checks.
- P = lighting load
- area = floor area
- load density = watts per square meter
Design current with continuous load Sizing
Idesign = Iload * 1.25
A practical planning factor for continuously loaded circuits.
- Idesign = design current
- Iload = connected load current
Formula finder scope
This surface is a practical lookup layer for recurring electrical equations, not a standards authority or a final design verifier.
Use this tool when
These are the practical situations where this workflow usually earns its keep.
You need a quick engineering check before a review meeting, coordination call, or field decision.
You want a lighter alternative to reopening a spreadsheet or full design package for a small recurring calculation.
You need a clearer intermediate output before the result moves into a formal calc sheet, report, or handover.
Design review preparation
Engineering utilities help teams show their reasoning quickly before a fuller design or calculation package is updated.
Field and coordination support
A browser-local calculator is useful when someone needs a quick answer in the middle of site coordination, troubleshooting, or team discussion.
Spreadsheet reduction
Many recurring checks do not need a sprawling workbook. A focused utility can reduce friction while still keeping the result visible and easy to challenge.
Common mistakes to avoid
These are the checks that usually keep the output useful instead of misleading.
Treating a quick calculator result as if it replaced the formal engineering record.
Forgetting to verify the assumptions, units, or code basis that sit behind the numbers.
Copying a result forward without leaving enough context for the next reviewer to understand it.
Learn how to use this tool
Search recurring electrical formulas locally instead of hunting through reference tabs or old notes. This guide is written for quick engineering sense-checks, not for pretending a browser widget replaces the formal design record.
Read the guideTell us what is missing
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