Dipole Calculator | Antenna Length Calculator (with Practical Examples) - OneSDR

Use this calculator to find the dimensions of a Dipole antenna [1] designed to operate at a specified wavelength or frequency.

A half-wave dipole antenna is comprised of two quarter-wavelength conductors placed end to end.

Calculator

Enter

The Operating Frequency
The Dipole Length as a function of its wavelength (λ) – one of the following options:
- λ/2
- λ
- 5λ/4
- 3λ/2

The tool will compute the antenna length (L).

Formula

The total length (L) of the dipole antenna in feet is calculated as:

L = 468 / f

where f is the frequency in MHz.

A dipole antenna is comprised of two arms of equal length

l = L/2

How to Calculate the Dipole Length

Enter the antenna’s frequency of operation with the appropriate units Hz/kHz/MHz/GHz.

The default configuration in the calculator is a half-wave dipole. However other lengths can be selected as well. The table below from Wikipedia shows the antenna gain as a function of wavelength.

Length as a function of λ	Antenna Gain* (dBi)	Notes
<<  λ/2	1.76	Poor efficiency
λ/2	2.15	Most common antenna
λ	4.0	Used only with fat dipoles
5λ/4	5.2	Highest gain
3λ/2	3.5	Can be used at third harmonic of λ/2
2λ	4.3	Not used

Antennas with length 2λ and higher are not used. As well, those with a length that’s less than λ/2 are not used either on account of poor efficiency.

Select the length as a function of wavelength.

Once these two parameters are entered, the physical length L of the dipole is provided.

📡 Antenna Gain is a function of Antenna Factor and wavelength

Example Calculations

To calculate the dimensions of a dipole antenna that operates at a certain frequency or wavelength.

If the frequency is specified then it can be entered directly into the calculator above. For example, at a frequency of operation equal to 1000 MHz, the dipole length (L) is 5.62 inches or 0.14 meters.

Instead we might want to specify the wavelength of the antenna in meters. A popular band of operation for amateur radio is the 2 meter (2m) band. Use this tool to convert from wavelength to frequency. In this case, the frequency is 150 MHz. The length of the half-wavelength dipole is 3.12 feet or 0.95 meters.

As the frequency of operation decreases, the physical length of the antenna increases.

In the above calculation for the 2 meter band antenna, we can see that the length of the antenna is 0.95 meters which is approximately half the wavelength. This is consistent with the fact that it is a half-wave dipole antenna.

The reason it’s not exactly half wavelength (1 meter in this case) is because of the end effect and a resulting multiplication by 0.95.

The actual formula for length (L) in feet of the half wave dipole is:

L = 492 / f

where f is the frequency in MHz.

Taking the end effect into account 492 * 0.95 ≈ 468.

Construction

The dipole antenna consists of two conductive elements. Hence the name dipole. The two elements are parallel to each other and separated by a gap.

Use this tool to calculate the Gap between the Antenna elements

The current flows through both conductors and causes the antenna to radiate, creating an RF signal that is radiated outward from the antenna. The radiation pattern is maximum in the direction perpendicular to the dipole.

A half wave dipole operating in the UHF band (300 MHz – 3 GHz) is shown in the picture below

Related Calculators

Monopole Antenna Length

Notes

Fesz has published a video on resonant dipoles where he discusses his simulations and practical measurements

Fesz demonstrates the influence of material thickness on the antenna bandwidth. Thinner the wire, the narrower the bandwidth.

Table of Wavelength vs Dipole Antenna Length

The following table provides the physical antenna dimensions (length in feet) as a function of the wavelength for a half wave dipole. For example, an antenna for 2 meter applications is 3.1 feet in length.

Antenna Wavelength (m)	Dipole Length (L) in feet
1	1.6
2	3.1
3	4.7
4	6.2
5	7.8
6	9.4
7	10.9
8	12.5
9	14.0
10	15.6
11	17.2
12	18.7
13	20.3
14	21.9
15	23.4
16	25.0
17	26.5
18	28.1
19	29.7
20	31.2
21	32.8
22	34.3
23	35.9
24	37.5
25	39.0
26	40.6
27	42.1
28	43.7
29	45.3
30	46.8
31	48.4
32	50.0
33	51.5
34	53.1
35	54.6
36	56.2
37	57.8
38	59.3
39	60.9
40	62.4
41	64.0
42	65.6
43	67.1
44	68.7
45	70.2
46	71.8
47	73.4
48	74.9
49	76.5
50	78.1
51	79.6
52	81.2
53	82.7
54	84.3
55	85.9
56	87.4
57	89.0
58	90.5
59	92.1
60	93.7
61	95.2
62	96.8
63	98.3
64	99.9
65	101.5
66	103.0
67	104.6
68	106.2
69	107.7
70	109.3
71	110.8
72	112.4
73	114.0
74	115.5
75	117.1
76	118.6
77	120.2
78	121.8
79	123.3
80	124.9
81	126.4
82	128.0
83	129.6
84	131.1
85	132.7
86	134.3
87	135.8
88	137.4
89	138.9
90	140.5
91	142.1
92	143.6
93	145.2
94	146.7
95	148.3
96	149.9
97	151.4
98	153.0
99	154.5
100	156.1
101	157.7
102	159.2
103	160.8
104	162.4
105	163.9
106	165.5
107	167.0
108	168.6
109	170.2
110	171.7
111	173.3
112	174.8
113	176.4
114	178.0
115	179.5
116	181.1
117	182.6
118	184.2
119	185.8
120	187.3
121	188.9
122	190.5
123	192.0
124	193.6
125	195.1
126	196.7
127	198.3
128	199.8
129	201.4
130	202.9
131	204.5
132	206.1
133	207.6
134	209.2
135	210.7
136	212.3
137	213.9
138	215.4
139	217.0
140	218.6
141	220.1
142	221.7
143	223.2
144	224.8
145	226.4
146	227.9
147	229.5
148	231.0
149	232.6
150	234.2
151	235.7
152	237.3
153	238.8
154	240.4
155	242.0
156	243.5
157	245.1
158	246.7
159	248.2
160	249.8
161	251.3
162	252.9
163	254.5
164	256.0
165	257.6
166	259.1
167	260.7
168	262.3
169	263.8
170	265.4
171	266.9
172	268.5
173	270.1
174	271.6
175	273.2
176	274.8
177	276.3
178	277.9
179	279.4
180	281.0
181	282.6
182	284.1
183	285.7
184	287.2
185	288.8
186	290.4
187	291.9
188	293.5
189	295.0
190	296.6
191	298.2
192	299.7
193	301.3
194	302.8
195	304.4
196	306.0
197	307.5
198	309.1
199	310.7
200	312.2

Table of Frequency vs Dipole Antenna Length

This table provides the length of a dipole antenna as a function of its frequency of operation. For example a 144 MHz dipole antenna is 3.3 feet in length.

Frequency (MHz)	Dipole Length (L) in Feet	Dipole Length (L) in Inches
1	468.0	5616.0
2	234.0	2808.0
3	156.0	1872.0
4	117.0	1404.0
5	93.6	1123.2
6	78.0	936.0
7	66.9	802.3
8	58.5	702.0
9	52.0	624.0
10	46.8	561.6
11	42.5	510.5
12	39.0	468.0
13	36.0	432.0
14	33.4	401.1
15	31.2	374.4
16	29.3	351.0
17	27.5	330.4
18	26.0	312.0
19	24.6	295.6
20	23.4	280.8
21	22.3	267.4
22	21.3	255.3
23	20.3	244.2
24	19.5	234.0
25	18.7	224.6
26	18.0	216.0
27	17.3	208.0
28	16.7	200.6
29	16.1	193.7
30	15.6	187.2
31	15.1	181.2
32	14.6	175.5
33	14.2	170.2
34	13.8	165.2
35	13.4	160.5
36	13.0	156.0
37	12.6	151.8
38	12.3	147.8
39	12.0	144.0
40	11.7	140.4
41	11.4	137.0
42	11.1	133.7
43	10.9	130.6
44	10.6	127.6
45	10.4	124.8
46	10.2	122.1
47	10.0	119.5
48	9.8	117.0
49	9.6	114.6
50	9.4	112.3
51	9.2	110.1
52	9.0	108.0
53	8.8	106.0
54	8.7	104.0
55	8.5	102.1
56	8.4	100.3
57	8.2	98.5
58	8.1	96.8
59	7.9	95.2
60	7.8	93.6
61	7.7	92.1
62	7.5	90.6
63	7.4	89.1
64	7.3	87.8
65	7.2	86.4
66	7.1	85.1
67	7.0	83.8
68	6.9	82.6
69	6.8	81.4
70	6.7	80.2
71	6.6	79.1
72	6.5	78.0
73	6.4	76.9
74	6.3	75.9
75	6.2	74.9
76	6.2	73.9
77	6.1	72.9
78	6.0	72.0
79	5.9	71.1
80	5.9	70.2
81	5.8	69.3
82	5.7	68.5
83	5.6	67.7
84	5.6	66.9
85	5.5	66.1
86	5.4	65.3
87	5.4	64.6
88	5.3	63.8
89	5.3	63.1
90	5.2	62.4
91	5.1	61.7
92	5.1	61.0
93	5.0	60.4
94	5.0	59.7
95	4.9	59.1
96	4.9	58.5
97	4.8	57.9
98	4.8	57.3
99	4.7	56.7
100	4.7	56.2
101	4.6	55.6
102	4.6	55.1
103	4.5	54.5
104	4.5	54.0
105	4.5	53.5
106	4.4	53.0
107	4.4	52.5
108	4.3	52.0
109	4.3	51.5
110	4.3	51.1
111	4.2	50.6
112	4.2	50.1
113	4.1	49.7
114	4.1	49.3
115	4.1	48.8
116	4.0	48.4
117	4.0	48.0
118	4.0	47.6
119	3.9	47.2
120	3.9	46.8
121	3.9	46.4
122	3.8	46.0
123	3.8	45.7
124	3.8	45.3
125	3.7	44.9
126	3.7	44.6
127	3.7	44.2
128	3.7	43.9
129	3.6	43.5
130	3.6	43.2
131	3.6	42.9
132	3.5	42.5
133	3.5	42.2
134	3.5	41.9
135	3.5	41.6
136	3.4	41.3
137	3.4	41.0
138	3.4	40.7
139	3.4	40.4
140	3.3	40.1
141	3.3	39.8
142	3.3	39.5
143	3.3	39.3
144	3.3	39.0
145	3.2	38.7
146	3.2	38.5
147	3.2	38.2
148	3.2	37.9
149	3.1	37.7
150	3.1	37.4
151	3.1	37.2
152	3.1	36.9
153	3.1	36.7
154	3.0	36.5
155	3.0	36.2
156	3.0	36.0
157	3.0	35.8
158	3.0	35.5
159	2.9	35.3
160	2.9	35.1
161	2.9	34.9
162	2.9	34.7
163	2.9	34.5
164	2.9	34.2
165	2.8	34.0
166	2.8	33.8
167	2.8	33.6
168	2.8	33.4
169	2.8	33.2
170	2.8	33.0
171	2.7	32.8
172	2.7	32.7
173	2.7	32.5
174	2.7	32.3
175	2.7	32.1
176	2.7	31.9
177	2.6	31.7
178	2.6	31.6
179	2.6	31.4
180	2.6	31.2
181	2.6	31.0
182	2.6	30.9
183	2.6	30.7
184	2.5	30.5
185	2.5	30.4
186	2.5	30.2
187	2.5	30.0
188	2.5	29.9
189	2.5	29.7
190	2.5	29.6
191	2.5	29.4
192	2.4	29.3
193	2.4	29.1
194	2.4	28.9
195	2.4	28.8
196	2.4	28.7
197	2.4	28.5
198	2.4	28.4
199	2.4	28.2
200	2.3	28.1
201	2.3	27.9
202	2.3	27.8
203	2.3	27.7
204	2.3	27.5
205	2.3	27.4
206	2.3	27.3
207	2.3	27.1
208	2.3	27.0
209	2.2	26.9
210	2.2	26.7
211	2.2	26.6
212	2.2	26.5
213	2.2	26.4
214	2.2	26.2
215	2.2	26.1
216	2.2	26.0
217	2.2	25.9
218	2.1	25.8
219	2.1	25.6
220	2.1	25.5
221	2.1	25.4
222	2.1	25.3
223	2.1	25.2
224	2.1	25.1
225	2.1	25.0
226	2.1	24.8
227	2.1	24.7
228	2.1	24.6
229	2.0	24.5
230	2.0	24.4
231	2.0	24.3
232	2.0	24.2
233	2.0	24.1
234	2.0	24.0
235	2.0	23.9
236	2.0	23.8
237	2.0	23.7
238	2.0	23.6
239	2.0	23.5
240	2.0	23.4
241	1.9	23.3
242	1.9	23.2
243	1.9	23.1
244	1.9	23.0
245	1.9	22.9
246	1.9	22.8
247	1.9	22.7
248	1.9	22.6
249	1.9	22.6
250	1.9	22.5
251	1.9	22.4
252	1.9	22.3
253	1.8	22.2
254	1.8	22.1
255	1.8	22.0
256	1.8	21.9
257	1.8	21.9
258	1.8	21.8
259	1.8	21.7
260	1.8	21.6
261	1.8	21.5
262	1.8	21.4
263	1.8	21.4
264	1.8	21.3
265	1.8	21.2
266	1.8	21.1
267	1.8	21.0
268	1.7	21.0
269	1.7	20.9
270	1.7	20.8
271	1.7	20.7
272	1.7	20.6
273	1.7	20.6
274	1.7	20.5
275	1.7	20.4
276	1.7	20.3
277	1.7	20.3
278	1.7	20.2
279	1.7	20.1
280	1.7	20.1
281	1.7	20.0
282	1.7	19.9
283	1.7	19.8
284	1.6	19.8
285	1.6	19.7
286	1.6	19.6
287	1.6	19.6
288	1.6	19.5
289	1.6	19.4
290	1.6	19.4
291	1.6	19.3
292	1.6	19.2
293	1.6	19.2
294	1.6	19.1
295	1.6	19.0
296	1.6	19.0
297	1.6	18.9
298	1.6	18.8
299	1.6	18.8
300	1.6	18.7

References

[1] Dipole Antennas on Wikipedia