Simple motor rated current calculator with calculation steps

Motor rated current also known as full load amperes (FLA) of a motor is the maximum current the motor windings are designed to carry. Here is a simple motor-rated current calculator.

Motor data input

Motor Type
Enter the motor rated voltage	V
Enter the motor rated power
Enter the motor Efficiency	95%
Enter the motor Power factor	0.85

Calculated Values
Motor rated current	A

How to use the motor-rated current calculator:

The above tool requires the following data for calculation:

Motor Type – Single-phase or three-phase. (Mandatory)
Motor-rated power in HP or kW. (Mandatory)
Input supply voltage. (Mandatory)
Motor Efficiency as per nameplate – (if known).
Rated power factor (if known).

After entering the required data, click on the “Calculate” button to find out the required fuse rating, Circuit Breaker rating, contactor current rating, and overload setting.

The appropriate selection of fuses, circuit breakers, overload relays, cables, and other switchgear is necessary to protect the motor from damage. The motor full load current forms the basis for the selection of all this equipment.

Motor-rated current calculation

For single-phase AC motors

For single-phase motors, when kW is known:

$F.L.C =\frac{P_k_W \times 1000}{Voltage \times cos \phi \times \eta}$

For single-phase motors, when HP is known:

$F.L.C =\frac{P_h_p \times 746}{Voltage \times cos \phi \times \eta}$

For Three-phase AC motors

For three phase motors, when kW is known:

$F.L.C =\frac{P_k_W \times 1000}{\surd3 \times Voltage \times cos \phi \times \eta}$

For three phase motors, when HP is known:

$F.L.C =\frac{P_h_p \times 746}{\surd3 \times Voltage \times cos \phi \times \eta}$

Where,

Voltage: The phase-to-phase voltage for a 3-phase supply.
Rating: The power rating of the motor in kW.
Power factor (cosΦ): The rated power factor of the motor.
Efficiency (η): The efficiency of the motor.

Single-phase motor rated current reference table:

		110V AC	220V AC	240V AC
0.07 kW	1/12	2.4	1.2	1.1
0.1 kW	1/8	3.3	1.6	1.5
0.12 kW	1/6	3.8	1.9	1.7
0.18 kW	1/4	4.5	2.3	2.1
0.25 kW	1/3	5.8	2.9	2.6
0.37 kW	1/2	7.9	3.9	3.6
0.56 kW	3/4	11	5.5	5
0.75 kW	1	15	7.3	6.7
1.1 kW	1.5	21	10	9
1.5 kW	2	26	13	12
2.2 kW	3	37	19	17
3 kW	4	49	24	22
3.7 kW	5	54	27	25
4 kW	5.5	60	30	27
5.5 kW	7.5	85	41	38
7.5 kW	10	110	55	50

Reference: https://www.rm-electrical.com/technical-resource/motor-current-charts/

Three-phase motor rated current reference table:

kW	HP	220V AC	240V AC	380V AC	415V AC	550V AC	660V AC	690V AC
0.1	1/8	0.32	0.30	0.19	0.17	0.13	0.11	0.10
0.18	¼	0.58	0.53	0.34	0.31	0.23	0.19	0.19
0.25	1/3	0.81	0.74	0.47	0.43	0.32	0.27	0.26
0.37	½	1.19	1.10	0.69	0.63	0.48	0.40	0.38
0.56	¾	1.81	1.66	1.05	0.96	0.72	0.60	0.58
0.75	1	2.42	2.22	1.40	1.28	0.97	0.81	0.77
1.1	1.40	3.55	3.26	2.06	1.88	1.42	1.18	1.13
1.5	2	5	4	3	3	2	2	2
2.2	3	7	7	4	4	3	2	2
3	4	10	9	6	5	4	3	3
3.7	5	12	11	7	6	5	4	4
4	5	13	12	7	7	5	4	4
5.5	7	18	16	10	9	7	6	6
7.5	10	24	22	14	13	10	8	8
9.3	12	30	28	17	16	12	10	10
10	13	32	30	19	17	13	11	10
11	14	36	33	21	19	14	12	11
15	19	48	44	28	26	19	16	15
18	23	58	53	34	31	23	19	19
22	28	71	65	41	38	28	24	23
30	38	97	89	56	51	39	32	31
37	47	119	110	69	63	48	40	38
45	57	145	133	84	77	58	48	46
55	70	178	163	103	94	71	59	57
75	95	242	222	140	128	97	81	77
90	115	291	266	168	154	116	97	93
110	140	355	326	206	188	142	118	113
130	165	420	385	243	223	168	140	134
150	191	484	444	280	257	183	161	154

*All the values above are approximated. The actual current may vary depending on the voltage, power factor, and motor efficiency.

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