Calculator Inputs
Loss Breakdown Graph
The bar chart separates each loss contributor. The marker trace compares received power, sensitivity, and total loss values.
Example Data Table
| Scenario | Tx Power | Distance | Rate | Connectors | Splices | Splitter | Total Planned Loss | Estimated Rx |
|---|---|---|---|---|---|---|---|---|
| Office fiber run | 4.00 dBm | 2.40 km | 0.35 dB/km | 4 × 0.40 dB | 2 × 0.10 dB | 3.50 dB | 8.64 dB | -4.64 dBm |
| Short coax segment | 8.00 dBm | 75.00 m | 0.06 dB/m | 2 × 0.25 dB | 0 × 0.00 dB | 0.00 dB | 5.80 dB | 2.20 dBm |
| Sensor cable path | 2.50 dBm | 350.00 ft | 0.01 dB/ft | 3 × 0.20 dB | 1 × 0.10 dB | 0.00 dB | 6.70 dB | -4.20 dBm |
Formula Used
Cable Loss = Distance × Attenuation Rate
Connector Loss = Connector Count × Connector Loss Each
Splice Loss = Splice Count × Splice Loss Each
Total Passive Loss = Cable + Connector + Splice + Splitter + Other
Total Planned Loss = Total Passive Loss + Design Margin
Estimated Received Power = Transmit Power − Total Planned Loss
Estimated Link Margin = Estimated Received Power − Receiver Sensitivity
Measured Loss = Transmit Power − Measured Received Power
Power Ratio Loss = 10 × log10(Input / Output)
Voltage or Current Loss = 20 × log10(Input / Output)
Power Delivered Percent = 10(−Total Passive Loss / 10) × 100
How to Use This Calculator
- Enter your transmit power in dBm.
- Add measured received power when real test data exists.
- Type the path distance and choose its unit.
- Enter attenuation rate using the same selected unit.
- Fill connector, splice, splitter, and other loss values.
- Add a design margin for aging, dirt, temperature, or growth.
- Provide receiver sensitivity to see remaining margin.
- Optionally enter linear input and output values for ratio loss.
- Press calculate to view results, exports, and the chart.
Frequently Asked Questions
1. What does dB loss measure?
dB loss measures how much signal weakens between two points. It expresses attenuation on a logarithmic scale, which makes very large or very small changes easier to compare across technical systems.
2. Why use dBm for transmit and receive power?
dBm is an absolute power reference tied to one milliwatt. It helps engineers compare actual source and received levels directly, then subtract losses and margins without converting many intermediate units.
3. What is the difference between passive loss and planned loss?
Passive loss includes physical attenuation sources such as cable, connectors, splices, splitters, and miscellaneous penalties. Planned loss adds extra design margin, giving a safer forecast for long-term performance.
4. When should I use the power ratio formula?
Use the power ratio formula when both input and output values represent power quantities, such as milliwatts or watts. The equation uses 10 times the base ten logarithm of input divided by output.
5. When should I use the voltage or current formula?
Use the voltage or current version when input and output are linear amplitudes measured under the same impedance. That formula uses 20 times the base ten logarithm of input divided by output.
6. Why is receiver sensitivity important?
Receiver sensitivity shows the lowest usable signal level for your equipment. Comparing estimated or measured received power against sensitivity reveals whether the link has enough operating margin to stay reliable.
7. How much design margin should I add?
The correct margin depends on environment, age, contamination risk, future growth, and reliability targets. Many designers add a modest reserve, then adjust it using manufacturer guidance and actual field conditions.
8. Can this calculator work for fiber, coax, or general signal paths?
Yes. The page uses user-defined attenuation and component losses, so it can estimate many technical paths. Accuracy depends on entering realistic rates, counts, and reference values for your specific hardware.