How many volts in 3 phase? The direct answer depends entirely on your regional grid standard and transformer topology, but the most common nominal values are 208V (North American commercial Wye), 240V (North American industrial Delta), and 400V (European/IEC Wye). There is no single universal 3-phase voltage. In a standard North American 120/208V Wye system, you will measure 208V line-to-line and 120V line-to-neutral. In a 277/480V commercial Wye system, you get 480V line-to-line. The voltage is fixed by the utility transformer, not derived from the load.
The Core Formula: Calculating 3-Phase Line-to-Line Voltage
To understand where 3-phase voltages come from, you have to look at the phase offset. In a Wye (Y) configured system, the three sine waves are offset by 120 electrical degrees. Because they do not peak at the same time, you cannot simply add the line-to-neutral voltages together (e.g., 120V + 120V does not equal 240V in a 3-phase Wye). Instead, you must use the square root of 3 ($\sqrt{3}$), which is approximately 1.732.
The governing formula for a Wye system is:
$V_{Line-to-Line} = V_{Line-to-Neutral} \times \sqrt{3}$
Let us substitute real-world values from a standard North American commercial panel:
$V_{L-L} = 120V \times 1.732 = 207.84V$
The electrical industry rounds this to a nominal 208V. This is why you cannot run a piece of equipment rated strictly for 240V on a 208V 3-phase panel without derating the motor or using a step-up transformer; you are roughly 13% short on voltage. For a deeper look at the vector math behind this 120-degree phase shift, the All About Circuits textbook chapter on Y-transformers provides excellent phasor diagrams.
Neighboring 3-Phase Voltages (±20% Reference Table)
Voltage on the jobsite is rarely a perfect textbook number. Utilities typically deliver power within a ±5% tolerance, and transformer taps can shift these values further. If we anchor our reference to the common 240V 3-phase industrial standard, a ±20% range gives us a band of 192V to 288V.
Here is how the standard nominal 3-phase line-to-line voltages stack up within and immediately adjacent to that band, detailing what you will actually read on your multimeter.
| Nominal 3-Phase (L-L) | Line-to-Neutral (Wye) | System Type | Common Application |
|---|---|---|---|
| 200V | N/A (Usually Delta) | Delta | Japanese industrial plants, legacy manufacturing |
| 208V | 120V | Wye (Y) | US commercial buildings, schools, strip malls |
| 230V | 133V | Delta / Wye | Utility delivery tolerance for 240V; Euro single-phase base |
| 240V | 120V (High-Leg) or N/A | Delta ($\Delta$) | US industrial motors, workshops, manufacturing |
| 250V | 144V | Wye / Delta | Marine, shipboard, and offshore platform power |
Note: In a 240V High-Leg (Stinger) Delta system, you have 240V line-to-line, but the line-to-neutral voltage on the high leg is 208V, not 120V. Never wire standard 120V control circuits to the high leg (typically the B-phase, colored orange per NEC 210.4).
120V vs 230V vs 3-Phase and the Power Factor Trap
A frequent point of confusion on the workbench is how voltage assumptions shift when moving between single-phase and 3-phase systems, and when attempting to convert power (kW) into electrical parameters.
How the Math Shifts: 120V vs 230V vs 3-Phase
- 120V (Single-Phase): This is a line-to-neutral measurement in North America. It utilizes one sine wave. Power is simply $P = V \times I$.
- 230V/240V (Single-Phase Split): In the US, this is two 120V legs 180 degrees out of phase (Line-to-Line). In Europe, 230V is the standard single-phase Line-to-Neutral voltage.
- 3-Phase: Introduces three sine waves offset by 120 degrees. The power delivery is continuous (no zero-crossing power drops), which is why 3-phase motors run smoother and draw less starting current. The $\sqrt{3}$ multiplier is mandatory for Wye L-L calculations and total power calculations.
When the Conversion is Meaningless: The Power Factor (PF) Trap
If you are searching for "how many volts" because you are actually trying to size a breaker or wire for a 3-phase motor or heater, you are likely confusing voltage with current. Voltage is a fixed system parameter; it does not scale with your load.
What you actually need to calculate is Amps, using the 3-phase power formula:
$I = \frac{P}{\sqrt{3} \times V \times PF}$
Here is where the conversion becomes meaningless if the Power Factor (PF) is unknown. If you have a 50 kW 3-phase load on a 480V system, and you assume a PF of 1.0 (purely resistive, like a heater), the current is 60.1A. But if that 50 kW load is an inductive motor array with a PF of 0.8, the current spikes to 75.2A.
If you guess the PF or assume it is 1.0, you will undersize your wire and breaker, leading to nuisance tripping or melted insulation. Always check the equipment nameplate for the exact PF or Full Load Amps (FLA) before sizing conductors. For practical measurement techniques, Fluke's guide on 3-phase power measurement details how to use a power analyzer to capture real-world PF on the jobsite.
Frequently Asked Questions About 3-Phase Voltage
How many volts is a 3-phase 480V system to ground?
In a standard 480Y/277V Wye system, the voltage from any phase to ground (neutral) is 277V ($480 \div 1.732$). This is why commercial lighting runs on 277V. However, if you are working on a 480V Delta system, there is no neutral. The voltage to ground is technically undefined (floating) unless one corner is intentionally grounded (Corner-Grounded Delta), in which case one phase will read 0V to ground, and the other two will read a full 480V to ground. Always verify with a meter before assuming a ground reference exists.
Can I get 120V from a 208V 3-phase panel?
Yes, absolutely. A 208V 3-phase panel is almost always a Wye configuration with a bonded neutral. By connecting a single-pole breaker to any of the three phases (A, B, or C) and routing the neutral to the neutral bar, you will get exactly 120V ($208 \div 1.732 = 120$). This is the standard method for powering standard office outlets and lighting in US commercial buildings.
Why does my multimeter read 230V on a nominal 240V 3-phase Delta system?
This is normal and expected. The NEC and utility standards typically allow a ±5% voltage tolerance at the point of delivery. Furthermore, utilities often set transformer taps to deliver slightly lower voltages (like 230V or 235V) to account for voltage drop over long feeder runs. By the time the voltage reaches a motor at the end of a 200-foot conduit run, it will have dropped back closer to the 240V nameplate requirement. If you read 230V at the main breaker lugs, your system is operating well within safe parameters.
