How many amps in 20 volts?

You cannot convert volts to amps directly — they measure different things. Volts are pressure; amps are flow rate. The current depends on the load: I = V / R (Ohm's Law). 20 V across a 10 Ω load → 2 A. 20 V across a 100 Ω load → 0.2 A. To get a definite answer you need the resistance OR the load power. Use the calculator above with mode "V and R" or "V and P".

How many amps in 3000 watts?

Depends on voltage and (for AC) power factor. DC or resistive AC: I = P/V. At 120 V → 25 A; at 240 V → 12.5 A; at 480 V → 6.25 A. AC with PF 0.85: divide further by 0.85: at 120 V → 29.4 A, at 240 V → 14.7 A. Three-phase 480 V at PF 0.85: I = 3000 / (√3 × 480 × 0.85) = 4.24 A. Higher voltage = lower current for the same power, which is why three-phase service uses smaller wires.

How many amps can 12 2 wire handle?

NEC ampacity for 12 AWG copper: 20 A at 60°C, 25 A at 75°C, 30 A at 90°C insulation (NEC Table 310.16). NEC 240.4(D) caps the breaker at 20 A regardless of insulation rating because of termination temperature limits — so 12-2 is rated 20 A maximum on a standard breaker. With derating for ambient or conductor count, the practical ampacity drops further. See the Wire Size Calculator for proper conductor selection.

How many amps in 1 volt?

Same answer as for any voltage: depends on the load. The relationship is set by Ohm's Law: I = V/R. 1 V across 1 Ω = 1 A; 1 V across 1 kΩ = 1 mA. Voltage and current are independent quantities — to find amps from a voltage, you also need either the resistance or the load power. The calculator above does this directly.

How many amps is 230 volts?

Same: depends on load. A 230 V residential circuit usually supplies 6–32 A (LED bulb 0.05 A, kettle 10 A, oven 20–30 A). The circuit breaker rating (typically 16 A or 20 A in EU residential) caps the maximum sustained current. To calculate for a specific load: I = P / V for resistive, I = P / (V·cos φ) for inductive. 3000 W on 230 V single-phase: I = 3000 / 230 = 13 A.

How many amps is 480 volts?

In three-phase 480 V, current depends on the load kVA: I = (kVA × 1000) / (√3 × 480). For 100 kVA → 120 A; for 500 kVA → 601 A. Common motor sizes: 50 HP at 0.85 PF, 92% efficiency draws ~57 A; 100 HP draws ~124 A (NEC 430.250 tabulates these). The 480 V three-phase is the dominant US commercial/industrial voltage because it delivers high kW at moderate amps, allowing smaller conductors than 240 V single-phase for the same load.

How many amps is 1000 watts at 120 volts?

I = 1000 / 120 = 8.33 A for a purely resistive (DC or AC PF=1.0) load. With AC at PF 0.85: I = 1000 / (120 × 0.85) = 9.8 A. A typical 1000 W appliance (microwave, toaster oven) on a 120 V US outlet draws ~8.3 A — well within the 15 A or 20 A breaker rating. NEC continuous-load rule (1.25×): if the load runs 3+ hours straight, the conductor must be sized for 8.3 × 1.25 = 10.4 A.

How many amps is 20 volts?

Same as "how many amps in 20 volts" — the answer depends on the connected load. 20 V across 10 Ω → 2 A; across 100 Ω → 0.2 A. To get a definite current, use Ohm's Law I = V/R or the power form I = P/V.

How to calculate full load amps?

For motors, FLA is on the nameplate — that's the most accurate value. To estimate from HP and voltage: FLA = (HP × 746) / (V × η × cos φ × √3) for three-phase, or without √3 for single-phase. NEC 430.250 tabulates standard FLA values by HP and voltage; conductors and breakers must be sized to the NEC table value, not the nameplate (with motors, the table values are deliberately conservative).

Calculator · Electrical · Amps · NEC 430.250 · Motor FLA

Amps calculator

Convert any combination of watts, volts, kVA, and HP to amps for DC, single-phase, or three-phase. Includes power factor, three-phase √3 factor, and NEC continuous-load rules. Worked examples and breaker-sizing reference. Reviewed by a licensed PE.

Use the amps calculator

Pick phase mode, then choose what you know — the calculator returns amps along with all related power quantities (kW, kVA, kVAR, HP, BTU/hr).

CALC.007 Universal Power · V · I · P · R · 3 modes · 6 solve combos

I know:[Given]

Voltage V[V]

Current I[I]

Power P[P]

Resistance R[R]

Pure DC: P = V · I. Resistance shown is V/I (Ohm's law equivalent).

Voltage V

— V

Current I

— A

Power P

— W

Resistance R

— Ω

Apparent power S: — kVA
Reactive power Q: — kVAR
Power factor used: —
Mechanical equivalent: — HP
Heat output: — BTU/hr

Show your work

P = V · I = ...

FORMULA · P = V · I (DC) SOURCE · OHM 1827 · IEEE STD 100

Amps — at a glance

Amps from watts and volts: I = P / V (DC or resistive). Example: 3000 W at 240 V = 12.5 A; at 120 V = 25 A.
Amps from kW (1-phase AC): A = 1000·kW / (V × PF). 5 kW at 230 V, PF 0.85 ≈ 25.6 A.
Amps from kW (3-phase AC): A = 1000·kW / (√3·V_LL·PF). 100 kW at 480 V, PF 0.9 ≈ 134 A.
Amps from horsepower: I = (HP × 746) / (V × η × cos φ) for 1-phase; ÷ √3 also for 3-phase. NEC 430.250 lists code values.
3000 watts at 240 V: Resistive: 12.5 A. At PF 0.85: 14.7 A. 3-phase 480 V at PF 0.85: 4.24 A.
12 AWG wire ampacity: 20 A breaker max per NEC 240.4(D). Raw NEC 310.16: 20/25/30 A at 60/75/90°C insulation.
Amps to ohms: Use Ohm's Law: R = V / I. 240 V and 8 A measured → R = 30 Ω.
Continuous-load rule: For loads ≥3 hr at full current, size conductor and breaker for 1.25 × FLA (NEC 210.19(A)).

The amps formula

Three forms depending on what you have. Pick the one that matches your inputs.

Eq. 01 — Ohm's Law (current from voltage and resistance) SI · Ohm 1827

I = \frac{V}{R}

I: current, A
V: voltage, V
R: resistance, Ω

Eq. 02 — Current from power SI · IEEE Std 100

I_{DC} = \frac{P}{V} \qquad I_{1\phi} = \frac{P}{V \cdot \cos\varphi} \qquad I_{3\phi} = \frac{P}{\sqrt{3} \cdot V_{LL} \cdot \cos\varphi}

P: active power, W, W
cos φ: power factor (1.0 for resistive), —

Eq. 03 — Current from kVA SI · NEMA standard

I_{1\phi} = \frac{kVA \cdot 1000}{V} \qquad I_{3\phi} = \frac{kVA \cdot 1000}{\sqrt{3} \cdot V_{LL}}

kVA: apparent power, kVA

Worked example: 30 A oven on 240 V

A typical residential electric oven draws 30 A on a 240 V single-phase circuit. Compute power, equivalent resistance, and the breaker / wire it requires.

Step	Calculation	Result
Power (resistive heater, PF = 1)	P = V × I = 240 × 30	7200 W = 7.2 kW
Equivalent resistance	R = V / I = 240 / 30	8.0 Ω
Continuous load (NEC 1.25×)	30 × 1.25	37.5 A required
Standard breaker (NEC 240.6)	round up 37.5 A	40 A breaker
Wire size (NEC Table 310.16, Cu 75°C)	40 A → minimum 8 AWG	8 AWG copper
Annual energy at 1 hr/day	7.2 × 365	2628 kWh / yr
Annual cost at $0.15/kWh	2628 × 0.15	$394 / yr

Note: even though the oven only draws 30 A, NEC requires sizing for 1.25× because it\'s a continuous load — that pushes you from a 30 A to a 40 A breaker and from 10 AWG to 8 AWG. Skipping this rule is one of the most common residential code violations.

How to calculate amps, step by step

Identify what you have. Voltage and resistance? Voltage and power? Power and power factor? Each combination uses a different form of the formula.
Pick the phase mode. DC for batteries and resistive loads. 1-phase AC for residential. 3-phase AC for commercial/industrial. The √3 factor enters only for 3-phase.
Apply the right formula. Ohm: I = V / R. Power form: I = P / V (DC), I = P / (V·cos φ) (1ph), I = P / (√3·V·cos φ) (3ph).
For motors, use FLA from the nameplate. Don't back-calculate motor amps from rated HP — actual FLA is on the nameplate and accounts for efficiency. NEC 430.250 also tabulates motor FLA by HP and voltage for design.
Apply NEC 1.25× for continuous loads. For loads operating 3+ hours at full current (most lighting, HVAC, motors), the conductor and breaker must be sized for 1.25 × FLA per NEC 210.19(A).
Round breaker up to standard size. NEC 240.6(A) standard sizes: 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150… Pick the smallest standard size ≥ load × 1.25.

Reference table — Amps for common voltage / power combinations

Watts → amps lookup, by voltage and phase

SOURCE · P / V relationship; PF = 1.0 (resistive)

Power	120V 1ph	240V 1ph	208V 3ph	480V 3ph
500 W	4.17 A	2.08 A	1.39 A	0.60 A
1000 W	8.33 A	4.17 A	2.78 A	1.20 A
1500 W	12.5 A	6.25 A	4.16 A	1.80 A
3000 W	25.0 A	12.5 A	8.33 A	3.61 A
5000 W	41.7 A	20.8 A	13.9 A	6.01 A
7500 W	62.5 A	31.3 A	20.8 A	9.02 A
10 000 W	83.3 A	41.7 A	27.8 A	12.0 A
25 000 W	208 A	104 A	69.4 A	30.1 A
50 000 W	417 A	208 A	139 A	60.1 A

For inductive loads, divide further by power factor (typical 0.80–0.90 for motors, 1.0 for resistive heaters).

Amps: comparison and differences

Term	Symbol	What it means	Where used
Full-load amps (FLA)	FLA	Steady-state current at rated load	Conductor and breaker sizing
Locked-rotor amps (LRA)	LRA	Current with rotor stalled (motor inrush)	HVAC, motor starting analysis
Inrush current	—	Initial current spike at energisation	Capacitor switching, motor start
Continuous current	—	Current sustained 3+ hours at rated	NEC 1.25× rule for sizing
Short-circuit current (SCA)	kA	Fault current available at a point	Breaker AIC sizing

Variants and special cases

Full-load amps (FLA)

The current the load draws at its rated operating point. Stamped on motor and equipment nameplates. NEC requires using the value from Table 430.250 (not the nameplate) for conductor sizing of motors — these table values are conservative.

Locked-rotor amps (LRA) and inrush

When a motor starts, it draws 5–8 × FLA for the first few cycles until the rotor accelerates. NEC 430 governs starter and breaker selection to handle this without nuisance tripping. The exact LRA is denoted by a "code letter" A–V on the nameplate.

Branch-circuit amps

Branch circuits supply individual outlets or fixed loads downstream of the last overcurrent device. Standard residential ratings: 15 A (lighting), 20 A (kitchen), 30 A (dryer), 50 A (range). NEC 210.20 governs OCPD selection: continuous + non-continuous ≤ breaker rating, with 1.25× factor on continuous portion.

Motor amps and breaker selection

Motor circuits use special rules (NEC 430): conductors sized for 1.25 × FLA; branch breaker can be 250% of FLA (instantaneous magnetic only) or 175–225% of FLA (inverse-time); overload protection is set at 115–125% of nameplate FLA. The unusually loose breaker tolerance accommodates motor inrush; overload protection prevents long-term burnout.

Amps quick reference — kW ↔ A, kVA ↔ A, HP ↔ A, oven and motor amps

Topic / question	Quick answer
Kilowatt amps calculator / kw amps	I = (kW × 1 000) / V (DC); ÷ (V × PF) for 1-φ; ÷ (√3 × V_LL × PF) for 3-φ. Use it for the 3kw in amps, 2.2kw in amps, 5.5kw in amps, 15 kw to amps, and 100 kw to amps lookups.
3kw in amps / 2.2kw in amps / 5.5kw in amps	Common motor sizes — 3 kW @ 230 V 1-φ PF 0.85 ≈ 15.4 A; 2.2 kW ≈ 11.3 A; 5.5 kW ≈ 28.1 A. For 3-phase 400 V PF 0.85 the same 5.5 kW draws ≈ 9.3 A.
15 kw to amps / 100 kw to amps	15 kW @ 480 V 3-φ PF 0.9 ≈ 20.0 A; 100 kW @ 480 V 3-φ PF 0.9 ≈ 133 A. Always include power factor for AC.
1 kva to amps	I = (kVA × 1 000) / V (1-φ) or ÷ (√3 × V_LL) (3-φ). 1 kVA at 230 V 1-φ = 4.35 A; at 400 V 3-φ = 1.44 A.
240 volts is how many amps	Depends on the load. 240 V × breaker rating gives the upper limit — 30 A breaker → up to 7 200 W resistive; 50 A breaker → up to 12 000 W; 100 A → up to 24 000 W.
How many amps is 480 volts / 230 volts / 1000 watts at 120 volts	Same dependency — at 1 000 W on 120 V resistive → 8.33 A. The PAA answers above cover the verbatim phrasings.
40 amps	A 40 A circuit on 240 V provides 9.6 kW resistive (or up to 8.16 kW at PF 0.85). Common use: electric range / oven branch (oven amps usually 30–50 A on #8 AWG copper).
Oven amps / hp amps chart	Oven amps run 25–50 A typical (240 V). HP amps chart per NEC 430.250: 1 HP @ 230 V 1-φ = 8 A; 5 HP = 28 A; 10 HP = 50 A; 25 HP @ 460 V 3-φ = 34 A.
FLA amps / full load amps / load amps calculator / full load amps calculator / locked rotor amps calculator	NEC 430.250 supersedes nameplate for FLA in conductor sizing. Locked-rotor (starting) amps are typically 5–8 × FLA per the NEMA Code Letter on the motor nameplate; the LRA calculator multiplies kVA/HP × HP × 1 000 / (√3 × V).
Amps to ohms	R = V / I (Ohm\'s Law). With 240 V and 8 A measured → R = 30 Ω. The same calculator above runs the conversion.
1 amps to volts / amps volts	Volts = amps × resistance. 1 A through a 12 Ω load drops 12 V; through 100 Ω drops 100 V. Like every "amps volts" question, you need a third quantity (R or P).
Amps per hour calculator	For batteries, amps per hour reduces to capacity / runtime: a 100 Ah battery at 5 A draws for 20 hours; at 50 A for 2 hours (Peukert effect aside). See battery runtime tool.

Related concepts on this site

Frequently asked questions

How many amps in 20 volts?: You cannot convert volts to amps directly — they measure different things. Volts are pressure; amps are flow rate. The current depends on the load: I = V / R (Ohm's Law). 20 V across a 10 Ω load → 2 A. 20 V across a 100 Ω load → 0.2 A. To get a definite answer you need the resistance OR the load power. Use the calculator above with mode "V and R" or "V and P".
How many amps in 3000 watts?: Depends on voltage and (for AC) power factor. DC or resistive AC: I = P/V. At 120 V → 25 A; at 240 V → 12.5 A; at 480 V → 6.25 A. AC with PF 0.85: divide further by 0.85: at 120 V → 29.4 A, at 240 V → 14.7 A. Three-phase 480 V at PF 0.85: I = 3000 / (√3 × 480 × 0.85) = 4.24 A. Higher voltage = lower current for the same power, which is why three-phase service uses smaller wires.
How many amps can 12 2 wire handle?: NEC ampacity for 12 AWG copper: 20 A at 60°C, 25 A at 75°C, 30 A at 90°C insulation (NEC Table 310.16). NEC 240.4(D) caps the breaker at 20 A regardless of insulation rating because of termination temperature limits — so 12-2 is rated 20 A maximum on a standard breaker. With derating for ambient or conductor count, the practical ampacity drops further. See the Wire Size Calculator for proper conductor selection.
How many amps in 1 volt?: Same answer as for any voltage: depends on the load. The relationship is set by Ohm's Law: I = V/R. 1 V across 1 Ω = 1 A; 1 V across 1 kΩ = 1 mA. Voltage and current are independent quantities — to find amps from a voltage, you also need either the resistance or the load power. The calculator above does this directly.
How many amps is 230 volts?: Same: depends on load. A 230 V residential circuit usually supplies 6–32 A (LED bulb 0.05 A, kettle 10 A, oven 20–30 A). The circuit breaker rating (typically 16 A or 20 A in EU residential) caps the maximum sustained current. To calculate for a specific load: I = P / V for resistive, I = P / (V·cos φ) for inductive. 3000 W on 230 V single-phase: I = 3000 / 230 = 13 A.
How many amps is 480 volts?: In three-phase 480 V, current depends on the load kVA: I = (kVA × 1000) / (√3 × 480). For 100 kVA → 120 A; for 500 kVA → 601 A. Common motor sizes: 50 HP at 0.85 PF, 92% efficiency draws ~57 A; 100 HP draws ~124 A (NEC 430.250 tabulates these). The 480 V three-phase is the dominant US commercial/industrial voltage because it delivers high kW at moderate amps, allowing smaller conductors than 240 V single-phase for the same load.
How many amps is 1000 watts at 120 volts?: I = 1000 / 120 = 8.33 A for a purely resistive (DC or AC PF=1.0) load. With AC at PF 0.85: I = 1000 / (120 × 0.85) = 9.8 A. A typical 1000 W appliance (microwave, toaster oven) on a 120 V US outlet draws ~8.3 A — well within the 15 A or 20 A breaker rating. NEC continuous-load rule (1.25×): if the load runs 3+ hours straight, the conductor must be sized for 8.3 × 1.25 = 10.4 A.
How many amps is 20 volts?: Same as "how many amps in 20 volts" — the answer depends on the connected load. 20 V across 10 Ω → 2 A; across 100 Ω → 0.2 A. To get a definite current, use Ohm's Law I = V/R or the power form I = P/V.
How to calculate full load amps?: For motors, FLA is on the nameplate — that's the most accurate value. To estimate from HP and voltage: FLA = (HP × 746) / (V × η × cos φ × √3) for three-phase, or without √3 for single-phase. NEC 430.250 tabulates standard FLA values by HP and voltage; conductors and breakers must be sized to the NEC table value, not the nameplate (with motors, the table values are deliberately conservative).

Sources and methodology

NFPA. National Electrical Code (NEC) NFPA 70, 2023. Articles 210.19(A), 240.4(D), 240.6(A), 310.16, 430.250.
IEEE. IEEE Std 100 — Authoritative Dictionary of IEEE Standards Terms, 7th Edition.
NEMA. NEMA MG 1 — Motors and Generators. Code-letter LRA designations.
BIPM. The International System of Units (SI), 9th Edition. Definition of the ampere.