RF Unit Converter
Instant conversions for power, frequency, length, temperature and dB — handy when reading US manuals and datasheets. 功率、频率、长度、温度、分贝即时换算——看美式手册和数据表时随手查。
Power功率
P(dBm) = 10 · log10(P / 1 mW) · P(dBW) = P(dBm) − 30 · P(W) = P(mW) / 1000公式：dBm 以 1 毫瓦为基准（0 dBm = 1 mW）；dBW 以 1 瓦为基准，比 dBm 小 30。
Frequency / Wavelength频率与波长互换
λ(m) = 299,792,458 / f(Hz) · shortcut: λ(m) ≈ 300 / f(MHz)公式：波长 = 光速 ÷ 频率；常用近似：波长(米) ≈ 300 ÷ 频率(MHz)。
Length长度
1 ft = 0.3048 m · 1 in = 2.54 cm · 1 mi = 1.609344 km公式：1 英尺 = 0.3048 米；1 英寸 = 2.54 厘米；1 英里 = 1.609344 公里。
Temperature温度
°F = °C × 9/5 + 32 · K = °C + 273.15公式：华氏度 = 摄氏度 × 9/5 + 32；开尔文 = 摄氏度 + 273.15。
dB Gain / Loss分贝换算
6 dB ≈ 4×
10 dB = 10×
20 dB = 100×
−3 dB ≈ ½×
dB = 10 · log10(power ratio) · ratio = 10^(dB/10) · example: 2× power = 3.01 dB公式：分贝 = 10 × log10(功率比)；功率比 = 10^(分贝/10)。例：功率翻倍 = 3.01 dB。注意：电压比用 20 × log10。
Practical notes / 实用说明： dBm is referenced to 1 milliwatt (0 dBm = 1 mW) — the standard unit for transmitter power and receiver sensitivity in ham datasheets. Wavelength uses the exact speed of light, 299,792,458 m/s. The dB converter above is for power ratios (10·log10); for voltage ratios use 20·log10.
dBm 以 1 毫瓦为基准（0 dBm = 1 mW），是火腿设备手册里发射功率和接收灵敏度的常用单位。波长计算使用精确光速 299,792,458 m/s。本页分贝换算针对功率比（10·log10），电压比请用 20·log10。
US manuals and datasheets love to mix units: power in dBm, wire lengths in feet and inches, temperatures in Fahrenheit, wavelengths implied rather than stated. This converter handles the five conversions a ham reaches for most — power, frequency/wavelength, length, temperature and dB — updating all outputs live as you type, no button to press.
The power card converts between dBm, dBW, watts and milliwatts. Remember the ladder: 0 dBm = 1 mW, +10 dB multiplies by ten, so 30 dBm = 1 W and a standard 100 W transmitter is +50 dBm. Receiver sensitivity figures like −123 dBm make sense on the same scale — that is about 5 × 10⁻¹³ watts, which is why dBm exists: nobody wants to count zeros.
The frequency card uses the exact speed of light (299,792,458 m/s) rather than the 300/MHz shortcut, so wavelength in metres, feet and inches is precise enough for cutting wire — though in practice your wire’s velocity factor moves the answer more than the rounding does. The dB card is deliberately power-only (10·log10); the formula note on the card reminds you that voltage ratios take 20·log10, the single most common dB mistake.
For deeper dives into the same quantities — voltage readings, S-units, ERP — the dB Calculator goes further, and dipole lengths live in the Antenna Calculator.
One habit worth building: always sanity-check a conversion against a number you already know. 20 m is about 65 feet; room temperature is 68 °F; half a wavelength on 20 metres is roughly 10 metres. If the converter disagrees with your instinct, check the input unit first — in practice, that is the cause almost every time.
Everything here updates instantly and offline, so it also works at the bench or in the field with no signal — bookmark it once and it stays useful.
Frequently asked questions
What does 0 dBm mean?
0 dBm is exactly 1 milliwatt. Every +10 dB multiplies by ten: 10 dBm = 10 mW, 20 dBm = 100 mW, 30 dBm = 1 W, 50 dBm = 100 W. Negative dBm values are fractions of a milliwatt — receiver sensitivity around −120 dBm is typical.
Should I use 300/MHz or the exact wavelength?
Use the 300 shortcut for quick wire math (300 / MHz gives metres to about 0.07% accuracy), and the exact c/f value when cutting an element to the millimetre, where the velocity factor of your wire matters more than the rounding anyway.
dBm or dBW — which should I use?
dBW is referenced to 1 watt, dBm to 1 milliwatt (0 dBW = 30 dBm). dBm dominates in ham and test-equipment practice; dBW appears in satellite link budgets. Subtracting 30 converts between them.
Is the dB converter the same for voltage?
No. dB here is a power ratio (10·log10). Voltage uses 20·log10 because power goes with voltage squared. A 2× voltage gain is +6 dB; a 2× power gain is +3 dB. Mixing them doubles your error.