Converter Inputs
Example Data
| Scenario | Input | Reference | Output | Mode |
|---|---|---|---|---|
| RF power level | 0 dBm | 1 mW | 1 mW | dBm → mW |
| Voltage gain | 2 V | 1 V | 6.0206 dB | V vs Vref → dB |
| Power increase | 2 W | 1 W | 3.0103 dB | P vs Pref → dB |
| Acoustic reference | 94 dB SPL | 0.00002 Pa | 1.0024 Pa | SPL → Pa |
Formulas Used
- dBm is referenced to 1 mW: mW = 10^(dBm/10)
- dBW is referenced to 1 W: W = 10^(dBW/10)
- dBV is referenced to 1 V: V = 10^(dBV/20)
- dBu is referenced to 0.775 V: V = 0.775·10^(dBu/20)
- dB SPL uses a reference pressure (often 20 µPa): p = Pref·10^(SPL/20)
How to Use This Calculator
- Select a conversion type that matches your measurement (power, voltage, or SPL).
- Enter the input value. Use a positive value when converting from linear units.
- If shown, enter the reference value. Keep it positive and realistic.
- Click Convert. Your result appears above the form.
- Use Download CSV or Download PDF for reporting.
Design targets and reference selection
Engineering reviews often start with a reference choice: 1 mW for dBm, 1 W for dBW, 1 V for dBV, 0.775 V for dBu, or 20 µPa for SPL. Consistent references prevent specification drift and let teams compare receiver sensitivity, amplifier gain, and acoustic exposure with the same scale. Record whether values are RMS or peak, and note bandwidth so each decibel label stays unambiguous.
Power conversions for RF and link budgets
When power is the conserved quantity, use 10·log10(P/Pref). A +3.0103 dB change equals doubling power, while −3.0103 dB halves it. For example, 10 dBm equals 10 mW, 20 dBm equals 100 mW, and 30 dBm equals 1 W, simplifying transmitter output and path-loss bookkeeping. A −90 dBm threshold is 1 picowatt, useful for sensitivity planning.
Voltage and amplitude measurements
Amplitude quantities use 20·log10(A/Aref) because power is proportional to amplitude squared. Doubling voltage across the same impedance produces +6.0206 dB, while a tenfold change is +20 dB. This matters in analog front ends, where gain blocks are specified in dB but probed in volts RMS. If impedance changes, convert to power first to avoid misinterpretation.
Dynamic range and noise floor tracking
Decibels make wide ranges manageable. A sensor with 120 dB dynamic range can resolve signals a million times smaller than its maximum. Converting between linear units and dB helps verify ADC headroom, quantify crest factor, and confirm that noise margins remain positive after filtering. Keep 10–12 dB of headroom for unexpected peaks, and validate SNR after cumulative gains and losses.
Acoustic level calculations
Sound pressure level uses 20·log10(p/Pref). With Pref = 0.00002 Pa, 94 dB SPL corresponds to about 1.002 Pa, a common calibrator setting. Use the SPL modes to translate microphone sensitivity curves into real pressure values for test reports. A 10 dB SPL increase represents about a 3.162× pressure ratio in the field.
Exportable outputs for documentation
CSV and PDF downloads support traceability. Store the chosen mode, input, reference, computed output, and formula alongside design notes. This reduces rework during audits and makes peer review faster, especially when multiple teams share measurement results across versions. Attach exports to lab notebooks and requirement matrices so decisions remain reproducible later for future verification.
FAQs
Why does power use 10 and voltage use 20?
Power ratios map directly to 10·log10(·). Voltage and other amplitudes relate to power squared, so the conversion becomes 20·log10(·) when impedance is unchanged.
Can decibel inputs be negative?
Yes. Negative dB values indicate levels below the chosen reference. The calculator accepts negative dB when converting to linear units like mW, W, V, or Pa.
What reference should I use for SPL?
Common practice uses 20 µPa (0.00002 Pa) in air. Enter your laboratory reference if your standard differs, then convert SPL to pressure or back.
Is dBu the same as dBV?
No. dBV references 1 V RMS, while dBu references 0.775 V RMS. The same measured voltage will yield different decibel values under these two systems.
When should I avoid voltage-to-dB calculations?
If impedance changes between measurement points, voltage ratios alone can mislead. Convert through power (or specify impedance) so the dB value reflects actual power transfer.
Why must linear inputs be positive?
Logarithms require a positive argument, so linear quantities like watts, volts, and pascals must be greater than zero. If you see an error, check units and sign.