Measure upload under realistic load
Run a sustained test from the streaming computer with normal household devices active. A fast download result is not an upload measurement. A brief speed-test peak also cannot prove that the connection will remain stable for a long broadcast.
Read the equation
For YouTube, the tool adds stereo audio to the video bitrate, multiplies for the number of outgoing streams and divides by 0.80. It then adds your household reserve. Dividing by 0.80 leaves 20% of the upload capacity outside the planned stream load; multiplying by 1.20 would leave a smaller fraction.
Choose a bitrate inside the codec range
H.264 uses YouTube’s published recommendation for the selected resolution and frame rate. AV1 and HEVC use published ranges, so you must choose a target inside that range. Use the target bitrate you plan to enter in OBS.
Watch the stream, not just the number
A passing calculation is a planning result. Encoder overload, Wi-Fi interference, packet loss, service throttling or other uploads can still interrupt a broadcast. Use the platform preview, movement and audio to check the actual output.
Choose the Twitch output in its own tools
For Twitch, set the output using Twitch’s broadcasting guide and run a test in Inspector. Start with the resolution and frame rate your upload can sustain, then watch for dropped frames and unstable bitrate. This calculator does not provide a numeric Twitch recommendation.
For the complete connection plan, use the streaming setup builder. You can keep older equipment in your plan.