Why does 8N1 use 10 bits per byte?

UART 8N1 includes 1 start bit, 8 data bits, and 1 stop bit, so each payload byte takes 10 serial bits.

UART Baud Rate & Packet Time Calculator

Estimate serial transmission time using baud rate, UART frame format, and payload size. Includes total bits, packet duration, and effective throughput.

Calculator

Inputs

Baud rate

Data bits Parity Stop bits

Payload bytes Packet count

Results

Frame format—

Bits per payload byte—

Total serial bits—

Time per packet—

Total transfer time—

Payload throughput—

Enter UART parameters.

How to estimate UART timing

UART duration is based on total transmitted bits and baud rate: time = total bits / baud. Total bits depend on frame format. For common 8N1, each payload byte uses 10 serial bits (1 start + 8 data + 1 stop).

FAQ

Does parity change throughput?

Yes. Parity adds one bit to each frame, increasing total transfer time for the same payload bytes.

Why is actual throughput lower than baud rate?

UART sends framing bits (start/stop/parity) in addition to payload bits, so payload throughput is always lower.