Wavelength / Frequency Converter
Convert between frequency and wavelength using c = λ × f, with half-wave and quarter-wave lengths for antenna design. Uses the exact speed of light c = 299,792,458 m/s.
- λ (m) = c / f (Hz)
- f (Hz) = c / λ (m)
- c = 299,792,458 m/s
Common band wavelengths
| Frequency | λ | λ/2 | λ/4 | Context |
|---|---|---|---|---|
| 700 MHz | 428.27494 mm | 214.13747 mm | 107.068735 mm | 700 MHz low-band (n28) |
| 900 MHz | 333.102731 mm | 166.551366 mm | 83.275683 mm | 900 MHz GSM / n8 |
| 1.80 GHz | 166.551366 mm | 83.275683 mm | 41.637841 mm | 1800 MHz / n3 |
| 2.10 GHz | 142.758313 mm | 71.379157 mm | 35.689578 mm | 2100 MHz / n1 |
| 2.60 GHz | 115.304792 mm | 57.652396 mm | 28.826198 mm | 2600 MHz / n7 |
| 3.50 GHz | 85.654988 mm | 42.827494 mm | 21.413747 mm | 3.5 GHz C-band (n78) |
| 3.70 GHz | 81.024989 mm | 40.512494 mm | 20.256247 mm | 3.7 GHz C-band (n77) |
| 5.90 GHz | 50.812281 mm | 25.406141 mm | 12.70307 mm | 5.9 GHz C-V2X |
| 24.25 GHz | 12.362576 mm | 6.181288 mm | 3.090644 mm | 24.25 GHz (n258 low) |
| 28.00 GHz | 10.706874 mm | 5.353437 mm | 2.676718 mm | 28 GHz mmWave (n257) |
| 39.00 GHz | 7.686986 mm | 3.843493 mm | 1.921747 mm | 39 GHz mmWave (n260) |
| 60.00 GHz | 4.996541 mm | 2.49827 mm | 1.249135 mm | 60 GHz unlicensed |
Why wavelength matters
Every antenna design, every array spacing, every RF enclosure resonance comes back to one number: the wavelength λ. For an electromagnetic wave travelling in free space, c = λ × f, where c is the exact speed of light, 299,792,458 m/s. Rearranging gives λ = c / f, so a 900 MHz GSM carrier has λ ≈ 333 mm, a 3.5 GHz C-band 5G carrier has λ ≈ 86 mm, and a 28 GHz mmWave carrier has λ ≈ 10.7 mm.
Antenna engineers care most about the half-wavelength (λ/2 dipole length) and the quarter-wavelength (monopole against a ground plane, matching stubs, RF chokes). In a massive MIMO panel the element spacing is typically λ/2, which explains why a 64-element panel at 3.5 GHz fits in a rack-sized enclosure while the same element count at 700 MHz would be enormous. At mmWave you can fit hundreds of elements into the same phone-sized module.
Who uses this calculator?
Antenna designers sizing dipoles, patches, microstrip stubs and Yagi elements. FWA and CPE integrators choosing antenna form factors. RF planners explaining to stakeholders why mmWave requires dense deployment. Students learning about propagation, diffraction, and why lower frequencies “bend” around buildings more easily.
Related tools
How to use this tool
- Enter a value. Type either a frequency or a wavelength.
- Pick the units. Select the input units (Hz/kHz/MHz/GHz or m/cm/mm).
- Read the conversion. See the converted value plus the λ/2 and λ/4 antenna lengths.
Frequently asked questions
- How do I convert frequency to wavelength?
- Use λ = c / f, where c is the speed of light (299,792,458 m/s) and f is the frequency in Hz. The tool handles the unit scaling for you, so you can enter GHz and read the wavelength in mm, cm or m without converting by hand.
- How long is the wavelength at 3.5 GHz?
- About 85.7 mm (0.0857 m), since λ = 299,792,458 / 3.5e9. At 28 GHz mmWave it shrinks to roughly 10.7 mm, which is why mmWave antenna elements are so small and arrays can pack many of them into a small panel.
- What are the half-wavelength and quarter-wavelength outputs for?
- λ/2 and λ/4 are common antenna dimensions: a half-wave dipole is about λ/2 long, and quarter-wave elements and matching stubs are about λ/4. Seeing them next to the wavelength gives you a quick first estimate for antenna sizing at a given frequency.
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