WireGaugeCalc Free calculator · NEC cited · works offline
Dc Voltage Drop Calculator
Dc voltage drop calculator is simple with WireGaugeCalc, since you enter the wire size, current, and one-way length and it returns the drop.
It doubles the run for the return conductor, because DC has no neutral, so both legs add resistance.
You see the volts lost and the percent drop right away, which tells you if the conductor holds the load within tolerance.
Open the calculatorUses Vd = (phase factor × K × I × L) / circular mils, K = 12.9 copper, 21.2 aluminum. Field aid only, verify against the current NEC and your local authority having jurisdiction.
How to Calculate Voltage Drop for a DC Circuit
DC drop depends on conductor resistance, the current, and the total wire path, so longer runs lose more voltage.
Since DC systems often run at 12V or 24V, even a small drop is a large percentage of the supply.
The calculator uses copper or aluminum resistance values, so the result matches the material on the reel.
Inputs the DC Voltage Drop Calculator Length and Current Need
Give the tool these values and it returns the drop:
- System voltage, such as 12V, 24V, or 48V
- Conductor size in AWG or kcmil
- Copper or aluminum conductor material
- Load current in amps
- One-way length of the run in feet
- Volts dropped and percent of supply lost
One app for every NEC calculation
WireGaugeCalc keeps the calculations you reach for most in one place:
- Voltage drop and wire sizing for any run
- Conduit fill for EMT, PVC, and RMC
- Box fill and junction box sizing
- Ampacity and temperature derating
- Motor circuit and load calculations
- Conduit bend offsets and saddles
Built for the field, works offline
The whole app runs on your phone, so it keeps working in a basement, an attic, or a job site with no signal.
There is no account to create and nothing to load. Open it, run the number, and get back to work.
- No signup and no signal needed
- Answers in a tap, not a spreadsheet
- Same tool on phone, tablet, and desktop
Every result cites the NEC article
Each answer shows the table or formula it came from, so you can check the method and learn the code as you go.
That makes the app useful on the job and during exam prep, since the reasoning is right next to the number.
Switch the code year your job runs on
Jurisdictions adopt the NEC at different times, so you can match the calculation to the code in force:
- NEC 2017, 2020, and 2023 tables
- Copper and aluminum conductors
- 60, 75, and 90 degree C terminations
- Single-phase and three-phase systems
Run the number, then get back to work
Stop flipping through a paper book or hopping between calculator sites. Enter your values, read the code-cited answer, and move on. Free to use, no signup.
Open the calculatorFrequently asked questions
Why does the calculator double the run length?
A DC circuit has no shared neutral, so the current returns on a second conductor. Both conductors add resistance, so the tool counts the round trip.
What percent drop is acceptable for a DC circuit?
Many low-voltage DC systems aim for 3 percent or less so the device sees enough voltage. The 3 percent branch-circuit guideline in the NEC is a recommendation, so check the current NEC and your local authority having jurisdiction for hard limits.
Does copper or aluminum change the result?
Yes, since aluminum has higher resistance per foot, an aluminum run drops more voltage than copper of the same size. Pick the right material in the dc volage drop calculator before you read the result.
Is WireGaugeCalc free to use?
Yes. Every calculator is free to run with no signup. A paid tier adds saved projects, PDF reports, and extra code years, but the core math stays free.
Does it work without internet?
Yes. The app runs on your device, so it keeps working with no signal on a job site, in a basement, or in an attic.
Are the results code accurate?
Results follow published NEC tables and standard formulas, and each answer shows the article it came from. It is a field aid, not a stamp of approval, so verify against the current code and your local authority before you wire anything.
Which NEC code year does it use?
You can switch between NEC 2017, 2020, and 2023, since jurisdictions adopt the code at different times. Pick the year your job runs on.