Rise Time Bandwidth Calculator
Convert between 10% to 90% rise time and approximate first-order bandwidth, including an input-tolerance range.
Input and tolerance
Select the quantity to calculate, then enter the known rise time or bandwidth.
Engineering notation is supported, including 500p, 1n, 350M, and 2.5G.
Nominal result and range
The result uses the common first-order relationship between 10% to 90% rise time and bandwidth.
The 0.35 constant is a first-order approximation for a single-pole response. Other response shapes, measurement definitions, probe loading, and interconnect effects can change the relationship.
Faster edges require a wider signal path
Rise time, not just clock frequency, determines how much high-frequency content a digital path must preserve. Use the estimate when selecting probes, oscilloscopes, connectors, and interconnect strategies.
Probe selection
A probe and oscilloscope need enough combined bandwidth to avoid materially slowing the observed edge.
Interconnect review
Fast edges make connector discontinuities, return paths, routing geometry, and termination more important.
Receiver capability
Check receiver bandwidth, input capacitance, thresholds, and setup or hold requirements after this estimate.
Equation, assumptions, and limits
For a first-order single-pole response, bandwidth is approximately 0.35 divided by the 10% to 90% rise time. A 1 ns edge therefore corresponds to about 350 MHz.
First-order model
The 0.35 factor assumes a single dominant pole and a 10% to 90% rise-time definition.
Response shape matters
Gaussian, multi-pole, underdamped, and bandwidth-limited systems can require a different constant or a fuller model.
Not a routing limit
The result does not determine whether a trace is electrically short or whether termination is required.
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Engineering reference
Equations, assumptions, and design guidance
Estimates equivalent single-pole bandwidth from 10% to 90% rise time, or rise time from bandwidth.
Equations and variables
BW * tr = 0.35- BW
- Equivalent bandwidth (Hz)
- tr
- 10% to 90% rise time (s)
Assumptions and limitations
Assumptions
- The response is dominated by one first-order pole.
- Rise time is measured between 10% and 90% of the settled step amplitude.
Limitations
- Higher-order responses, overshoot, slew-rate limiting, and measurement-system bandwidth can make the 0.35 relationship inaccurate.
Worked example and design use
10 ns rise time
Inputs: tr = 10 ns
Outputs: Equivalent bandwidth = 35 MHz
Design guidance
- Treat the result as an initial bandwidth target, then verify the complete signal chain and waveform response.