周波数⇔波長 変換ツール
速度係数を考慮した変換
Required Parameters
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Quick Answer
Wavelength (λ) = Velocity / Frequency. In a vacuum, velocity is the speed of light (c). In a cable or PCB, waves travel slower, requiring a Velocity Factor (VF) between 0.5 and 0.9.
Frequency to Period Calculator
Convert frequency to period instantly with T = 1/f — enter Hz, kHz, MHz, or GHz and get period in seconds (auto-scaled to ms, µs, or ns). Switch to Frequency (from period) to solve the reverse.
Quick start: Select Period, enter frequency (e.g. 1 MHz) → result shows 1 µs. Select Frequency (from period), enter 16.67 ms → 60 Hz.
Frequency to period formula
T = 1 / f
| Symbol | Unit | Meaning |
|---|---|---|
| T | seconds (s) | Time for one complete cycle |
| f | hertz (Hz) | Cycles per second |
Reverse: f = 1 / T
Common conversions
| Frequency | Period |
|---|---|
| 60 Hz (mains US) | 16.67 ms |
| 50 Hz (mains EU) | 20 ms |
| 1 kHz | 1 ms |
| 1 MHz | 1 µs |
| 1 GHz | 1 ns |
| 2.4 GHz (WiFi) | 417 ps |
Worked example
Find period of 100 MHz clock:
- T = 1 / 100,000,000 = 10 ns
- Half-period (for edge timing) = 5 ns
Period vs wavelength
Period is time per cycle; wavelength is distance per cycle:
λ = c × T = c / f
For RF wavelength with velocity factor, use the Frequency to Wavelength Calculator.
Related tools
- Frequency to Wavelength Calculator — λ = c/f with velocity factor
- 555 Timer Calculator — astable period from R and C
- RC Time Constant Calculator
- Reactance Calculator
Design Notes
Never assume signals travel at the speed of light over a PCB or through a coaxial cable. For example, standard FR4 PCB material has a VF of roughly 0.45 to 0.55 depending on the trace geometry. This means a 1 GHz signal, which has a 30 cm wavelength in air, will only have a ~15 cm wavelength on your PCB. If you are designing quarter-wave matching stubs or length-matching high speed lines, using the correct velocity factor is critical.
Common Mistakes
- 1
Using c (300,000 km/s) for calculations inside coax cables. RG-58 coax typically has a VF of 0.66, meaning the wave is 34% slower.
- 2
Confusing Hz with MHz/GHz resulting in calculation errors off by millions. Always use base SI units or keep track of the scientific notation.
- 3
Ignoring the effect of dielectric loading. Exposing a trace to air vs encapsulating it in conformal coating changes the local velocity factor.
Engineering Handbox
1. Convert Frequency: 2.4 GHz = 2,400,000,000 Hz 2. Base Wavelength (Air): λ = c / f = 299,792,458 / 2.4e9 = 12.49 cm 3. Apply Velocity Factor: 12.49 cm × 0.66 = 8.24 cm
Knowledge Base
波長の公式は？
λ = c / f。媒質中では λ = (c × VF) / f。例：2.4GHz自由空間 = 12.5cm。
速度係数とは？
媒質中の伝搬速度と光速の比。FR4 PCB ≈ 0.45〜0.55、RG-58同軸 = 0.66。VF = 1/√εr。
なぜ波長が電子回路で重要？
回路寸法がλ/10に達すると伝送線路効果（反射、定在波、インピーダンス整合）が支配的に。
アンテナ長の計算は？
半波長ダイポール：L = c/(2f)。四分の一波長モノポール：L = c/(4f)。
2.4GHz WiFiの波長は？
自由空間：12.5cm。PCB上（VF≈0.5）：約6.25cm。四分の一波長アンテナ：約3.1cm。
Related Engineering Tools
Frequency to Wavelength Conversion
Convert frequency and wavelength with velocity factor
555 Timer Calculator
Monostable and astable timing
Reactance Calculator
Inductive and capacitive reactance
Low Pass / High Pass Filter Calculator
-3 dB cutoff for RC and RL filters
Time Constant Calculator
RC and RL transient constant