DB9 to DB25 Conversion Pinout

Written by Michael Cone

Updated at January 26th, 2026

+ More

Pinout and COM Port Summary Card

EIA-232-E (RS-232)
Function

PIN #
DB-25	DB-9

EIA-530
Function

PIN #
DB-25

TO
DTE

TO
DCE

Shield

1

Shield

1

Transmit Data (TD)

2

3

Transmit Data	(A)
	(B)

2
14

>

Receive Data (RD)

3

2

Receive Data	(A)
	(B)

3
16

<

Request To Send (RTS)

4

7

Request To Send	(A)
	(B)

4
19

>

Clear To Send (CTS)

5

8

Clear To Send	(A)
	(B)

5
13

<

DCE Ready (DSR)

6

6

DCE Ready	(A)
	(B)

6
22

<

Signal Ground (SG)

7

5

Signal Ground

(A)

7

Received Line Signal Detector (DCD)

8

1

Received Line Signal Detector	(A)
	(B)

8
10

<

DTE Ready (DTR)

20

4

DTE Ready	(A)
	(B)

20
23

>

Ring Indicator

22

9

N/A

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This table is from http://www.bb-elec.com/Learning-Center/All-White-Papers/Serial/Quick-Reference-Card-RS-232-DB9-DB25-pinouts-level.aspx

connector pinout