How do you convert octal to decimal?

To convert octal to decimal, multiply each octal digit by 8 raised to the power of its position (starting from 0 at the rightmost digit) and sum all the results.

What is the decimal equivalent of octal 100?

Octal 100 evaluates to (1 × 8^2) + (0 × 8^1) + (0 × 8^0), which equals decimal 64.

Can I convert decimal numbers back to octal?

Yes. Switch the converter mode to Decimal to Octal, paste your base-10 integer, and the tool will instantly calculate the octal string.

Is my data stored or transmitted to any server?

No. The entire conversion process executes 100% locally in your web browser using JavaScript. Zero data is transmitted to or stored on any server.

Octal to Decimal Converter: Base-8 to Base-10

Octal to Decimal Converter

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Tip: enter one number to see the digit-by-digit steps, binary and hex. Several numbers (one per line), octal fractions like 56.3 and prefixes like 0o17 also work.

Output Read as Width Split on 1,000 separators

Output appears here

Tool Name	Explanation
Related Developer Tools
Decimal to Octal Converter	Converts decimal numbers into base-8 octal representation with step-by-step division.
Hex to Octal Converter	Converts hexadecimal numbers into octal by mapping hex digits through binary equivalents.
Binary to Text Converter	Decodes binary (0s and 1s) back into clean, readable text.
Text to Binary Converter	Converts text strings into 8-bit or 7-bit binary representation.
Text to Hex Converter	Converts plain text characters into hexadecimal ASCII or UTF-8 values.
Hex to Text Converter	Decodes hexadecimal values back into plain, human-readable text.
Text to Octal Converter	Converts text into octal bytes with separator, digits, and prefix options.
Octal to Text Converter	Decodes octal byte sequences back into readable plain text.
Decimal to Binary Converter	Converts decimal numbers into binary with step-by-step logic and 2's complement.
Binary to Decimal Converter	Converts binary numbers into decimal integers with full positional notation.
Hex to Binary Converter	Converts base-16 hexadecimal numbers directly into base-2 binary strings.
Binary to Hex Converter	Groups binary digits into 4-bit nibbles and converts them to hex digits.
Octal to Binary Converter	Converts base-8 octal values directly into equivalent binary groups.
Binary to Octal Converter	Groups binary bits in sets of three to convert directly into octal numbers.
Hex to Decimal Converter	Converts base-16 hexadecimal values into base-10 decimal numbers using positional values.
Decimal to Hex Converter	Converts base-10 decimal numbers into base-16 hexadecimal with steps and prefix options.

Example 1: Convert 755 to Decimal

Position	Octal digit	Power of 8	Digit x Power of 8
2	7	8^2	448
1	5	8^1	40
0	5	8^0	5

Add the last column: 448 + 40 + 5 = 493.

Example 2: Convert 153 to Decimal

Position	Octal digit	Power of 8	Digit x Power of 8
2	1	8^2	64
1	5	8^1	40
0	3	8^0	3

Add the last column: 64 + 40 + 3 = 107.

Octal Digit to Decimal Table (0-7)

Octal digit	Decimal	Binary (3-bit)
0	0	`000`
1	1	`001`
2	2	`010`
3	3	`011`
4	4	`100`
5	5	`101`
6	6	`110`
7	7	`111`

Octal to Decimal Table (000-377)

Octal (3-digit)	Decimal	Binary (8-bit)	Hex
000	0	`00000000`	`00`
001	1	`00000001`	`01`
002	2	`00000010`	`02`
003	3	`00000011`	`03`
004	4	`00000100`	`04`
005	5	`00000101`	`05`
006	6	`00000110`	`06`
007	7	`00000111`	`07`
010	8	`00001000`	`08`
011	9	`00001001`	`09`
012	10	`00001010`	`0A`
013	11	`00001011`	`0B`
014	12	`00001100`	`0C`
015	13	`00001101`	`0D`
016	14	`00001110`	`0E`
017	15	`00001111`	`0F`
020	16	`00010000`	`10`
021	17	`00010001`	`11`
022	18	`00010010`	`12`
023	19	`00010011`	`13`
024	20	`00010100`	`14`
025	21	`00010101`	`15`
026	22	`00010110`	`16`
027	23	`00010111`	`17`
030	24	`00011000`	`18`
031	25	`00011001`	`19`
032	26	`00011010`	`1A`
033	27	`00011011`	`1B`
034	28	`00011100`	`1C`
035	29	`00011101`	`1D`
036	30	`00011110`	`1E`
037	31	`00011111`	`1F`
040	32	`00100000`	`20`
041	33	`00100001`	`21`
042	34	`00100010`	`22`
043	35	`00100011`	`23`
044	36	`00100100`	`24`
045	37	`00100101`	`25`
046	38	`00100110`	`26`
047	39	`00100111`	`27`
050	40	`00101000`	`28`
051	41	`00101001`	`29`
052	42	`00101010`	`2A`
053	43	`00101011`	`2B`
054	44	`00101100`	`2C`
055	45	`00101101`	`2D`
056	46	`00101110`	`2E`
057	47	`00101111`	`2F`
060	48	`00110000`	`30`
061	49	`00110001`	`31`
062	50	`00110010`	`32`
063	51	`00110011`	`33`
064	52	`00110100`	`34`
065	53	`00110101`	`35`
066	54	`00110110`	`36`
067	55	`00110111`	`37`
070	56	`00111000`	`38`
071	57	`00111001`	`39`
072	58	`00111010`	`3A`
073	59	`00111011`	`3B`
074	60	`00111100`	`3C`
075	61	`00111101`	`3D`
076	62	`00111110`	`3E`
077	63	`00111111`	`3F`
100	64	`01000000`	`40`
101	65	`01000001`	`41`
102	66	`01000010`	`42`
103	67	`01000011`	`43`
104	68	`01000100`	`44`
105	69	`01000101`	`45`
106	70	`01000110`	`46`
107	71	`01000111`	`47`
110	72	`01001000`	`48`
111	73	`01001001`	`49`
112	74	`01001010`	`4A`
113	75	`01001011`	`4B`
114	76	`01001100`	`4C`
115	77	`01001101`	`4D`
116	78	`01001110`	`4E`
117	79	`01001111`	`4F`
120	80	`01010000`	`50`
121	81	`01010001`	`51`
122	82	`01010010`	`52`
123	83	`01010011`	`53`
124	84	`01010100`	`54`
125	85	`01010101`	`55`
126	86	`01010110`	`56`
127	87	`01010111`	`57`
130	88	`01011000`	`58`
131	89	`01011001`	`59`
132	90	`01011010`	`5A`
133	91	`01011011`	`5B`
134	92	`01011100`	`5C`
135	93	`01011101`	`5D`
136	94	`01011110`	`5E`
137	95	`01011111`	`5F`
140	96	`01100000`	`60`
141	97	`01100001`	`61`
142	98	`01100010`	`62`
143	99	`01100011`	`63`
144	100	`01100100`	`64`
145	101	`01100101`	`65`
146	102	`01100110`	`66`
147	103	`01100111`	`67`
150	104	`01101000`	`68`
151	105	`01101001`	`69`
152	106	`01101010`	`6A`
153	107	`01101011`	`6B`
154	108	`01101100`	`6C`
155	109	`01101101`	`6D`
156	110	`01101110`	`6E`
157	111	`01101111`	`6F`
160	112	`01110000`	`70`
161	113	`01110001`	`71`
162	114	`01110010`	`72`
163	115	`01110011`	`73`
164	116	`01110100`	`74`
165	117	`01110101`	`75`
166	118	`01110110`	`76`
167	119	`01110111`	`77`
170	120	`01111000`	`78`
171	121	`01111001`	`79`
172	122	`01111010`	`7A`
173	123	`01111011`	`7B`
174	124	`01111100`	`7C`
175	125	`01111101`	`7D`
176	126	`01111110`	`7E`
177	127	`01111111`	`7F`
200	128	`10000000`	`80`
201	129	`10000001`	`81`
202	130	`10000010`	`82`
203	131	`10000011`	`83`
204	132	`10000100`	`84`
205	133	`10000101`	`85`
206	134	`10000110`	`86`
207	135	`10000111`	`87`
210	136	`10001000`	`88`
211	137	`10001001`	`89`
212	138	`10001010`	`8A`
213	139	`10001011`	`8B`
214	140	`10001100`	`8C`
215	141	`10001101`	`8D`
216	142	`10001110`	`8E`
217	143	`10001111`	`8F`
220	144	`10010000`	`90`
221	145	`10010001`	`91`
222	146	`10010010`	`92`
223	147	`10010011`	`93`
224	148	`10010100`	`94`
225	149	`10010101`	`95`
226	150	`10010110`	`96`
227	151	`10010111`	`97`
230	152	`10011000`	`98`
231	153	`10011001`	`99`
232	154	`10011010`	`9A`
233	155	`10011011`	`9B`
234	156	`10011100`	`9C`
235	157	`10011101`	`9D`
236	158	`10011110`	`9E`
237	159	`10011111`	`9F`
240	160	`10100000`	`A0`
241	161	`10100001`	`A1`
242	162	`10100010`	`A2`
243	163	`10100011`	`A3`
244	164	`10100100`	`A4`
245	165	`10100101`	`A5`
246	166	`10100110`	`A6`
247	167	`10100111`	`A7`
250	168	`10101000`	`A8`
251	169	`10101001`	`A9`
252	170	`10101010`	`AA`
253	171	`10101011`	`AB`
254	172	`10101100`	`AC`
255	173	`10101101`	`AD`
256	174	`10101110`	`AE`
257	175	`10101111`	`AF`
260	176	`10110000`	`B0`
261	177	`10110001`	`B1`
262	178	`10110010`	`B2`
263	179	`10110011`	`B3`
264	180	`10110100`	`B4`
265	181	`10110101`	`B5`
266	182	`10110110`	`B6`
267	183	`10110111`	`B7`
270	184	`10111000`	`B8`
271	185	`10111001`	`B9`
272	186	`10111010`	`BA`
273	187	`10111011`	`BB`
274	188	`10111100`	`BC`
275	189	`10111101`	`BD`
276	190	`10111110`	`BE`
277	191	`10111111`	`BF`
300	192	`11000000`	`C0`
301	193	`11000001`	`C1`
302	194	`11000010`	`C2`
303	195	`11000011`	`C3`
304	196	`11000100`	`C4`
305	197	`11000101`	`C5`
306	198	`11000110`	`C6`
307	199	`11000111`	`C7`
310	200	`11001000`	`C8`
311	201	`11001001`	`C9`
312	202	`11001010`	`CA`
313	203	`11001011`	`CB`
314	204	`11001100`	`CC`
315	205	`11001101`	`CD`
316	206	`11001110`	`CE`
317	207	`11001111`	`CF`
320	208	`11010000`	`D0`
321	209	`11010001`	`D1`
322	210	`11010010`	`D2`
323	211	`11010011`	`D3`
324	212	`11010100`	`D4`
325	213	`11010101`	`D5`
326	214	`11010110`	`D6`
327	215	`11010111`	`D7`
330	216	`11011000`	`D8`
331	217	`11011001`	`D9`
332	218	`11011010`	`DA`
333	219	`11011011`	`DB`
334	220	`11011100`	`DC`
335	221	`11011101`	`DD`
336	222	`11011110`	`DE`
337	223	`11011111`	`DF`
340	224	`11100000`	`E0`
341	225	`11100001`	`E1`
342	226	`11100010`	`E2`
343	227	`11100011`	`E3`
344	228	`11100100`	`E4`
345	229	`11100101`	`E5`
346	230	`11100110`	`E6`
347	231	`11100111`	`E7`
350	232	`11101000`	`E8`
351	233	`11101001`	`E9`
352	234	`11101010`	`EA`
353	235	`11101011`	`EB`
354	236	`11101100`	`EC`
355	237	`11101101`	`ED`
356	238	`11101110`	`EE`
357	239	`11101111`	`EF`
360	240	`11110000`	`F0`
361	241	`11110001`	`F1`
362	242	`11110010`	`F2`
363	243	`11110011`	`F3`
364	244	`11110100`	`F4`
365	245	`11110101`	`F5`
366	246	`11110110`	`F6`
367	247	`11110111`	`F7`
370	248	`11111000`	`F8`
371	249	`11111001`	`F9`
372	250	`11111010`	`FA`
373	251	`11111011`	`FB`
374	252	`11111100`	`FC`
375	253	`11111101`	`FD`
376	254	`11111110`	`FE`
377	255	`11111111`	`FF`

Octal Place Values (Powers of 8)

Position	Power of 8	Place value	Octal value
0	8^0	1	`1`
1	8^1	8	`10`
2	8^2	64	`100`
3	8^3	512	`1000`
4	8^4	4096	`10000`
5	8^5	32768	`100000`
6	8^6	262144	`1000000`
7	8^7	2097152	`10000000`
8	8^8	16777216	`100000000`
9	8^9	134217728	`1000000000`
10	8^10	1073741824	`10000000000`

Common Octal Numbers in Decimal

Number	Octal	Decimal
Subnet mask octet (/25)	`200`	128
Subnet mask octet (/26)	`300`	192
Subnet mask octet (/27)	`340`	224
Subnet mask octet (/28)	`360`	240
Subnet mask octet (/29)	`370`	248
Subnet mask octet (/30)	`374`	252
Subnet mask octet (/31)	`376`	254
Subnet mask octet (/24)	`377`	255
SSH port	`26`	22
SMTP port	`31`	25
DNS port	`65`	53
HTTP port	`120`	80
HTTPS port	`673`	443
MySQL port	`6352`	3306
PostgreSQL port	`12470`	5432
Alternate HTTP port	`17620`	8080
Loopback first octet	`177`	127
Private IP first octet (10.x.x.x)	`12`	10
Private IP first octet (192.168.x.x)	`300`	192
Private IP second octet (192.168.x.x)	`250`	168
Ten	`12`	10
One hundred	`144`	100
One thousand	`1750`	1000
Max signed 8-bit	`177`	127
Max unsigned 8-bit	`377`	255
Values in a byte	`400`	256
One kibibyte	`2000`	1024
Page size	`10000`	4096
Max signed 16-bit	`77777`	32767
Max unsigned 16-bit	`177777`	65535
Values in 16 bits	`200000`	65536
Max RGB hex FFFFFF	`77777777`	16777215
Max signed 32-bit	`17777777777`	2147483647
Max unsigned 32-bit	`37777777777`	4294967295
Days from 1970 to 2000	`25315`	10957
ASCII letter A	`101`	65
ASCII letter a	`141`	97
ASCII digit 0	`60`	48
ASCII space	`40`	32
ASCII line feed	`12`	10

Common chmod Modes: Octal to Decimal

Octal mode	Decimal	Symbolic	Use
755	493	`rwxr-xr-x`	Executables, directories
644	420	`rw-r--r--`	Regular files
777	511	`rwxrwxrwx`	Everyone full access
600	384	`rw-------`	Private file
700	448	`rwx------`	Private directory or script
664	436	`rw-rw-r--`	Group writable file
750	488	`rwxr-x---`	Group can read and run
640	416	`rw-r-----`	Group can read
444	292	`r--r--r--`	Read only for all
775	509	`rwxrwxr-x`	Group writable directory

Octal to Signed Decimal (Two's Complement)

Octal	Unsigned decimal	Signed decimal	Bits
`000`	0	0	8
`001`	1	1	8
`176`	126	126	8
`177`	127	127	8
`200`	128	-128	8
`201`	129	-127	8
`307`	199	-57	8
`366`	246	-10	8
`373`	251	-5	8
`376`	254	-2	8
`377`	255	-1	8
`77777`	32767	32767	16
`100000`	32768	-32768	16
`177773`	65531	-5	16
`177777`	65535	-1	16
`20000000000`	2147483648	-2147483648	32
`37777777777`	4294967295	-1	32

Octal Fractions in Decimal

Octal	Decimal
`0.4`	0.5
`0.2`	0.25
`0.1`	0.125
`0.04`	0.0625
`0.5`	0.625
`0.54`	0.6875
`1.4`	1.5
`2.2`	2.25
`12.3`	10.375
`56.3`	46.375
`153.7`	107.875
`377.377`	255.498046875
`0.063`	0.099609375
`7.7`	7.875

Technical Q&A / FAQ Matrix

Technical Developer Question	Exact Solution & Code Snippet
How do I convert octal to decimal in JavaScript?	`parseInt('755', 8)`
How do I convert octal to decimal in Python?	`int('755', 8)`
How do I convert octal to decimal in Go?	`strconv.ParseInt("755", 8, 64)`
How do I convert octal to decimal in Java?	`Integer.parseInt("755", 8)`
How do I convert octal to decimal in C#?	`Convert.ToInt32("755", 8)`
How do I convert octal to decimal in PHP?	`echo octdec('755');`
How do I convert octal to decimal in Rust?	`i64::from_str_radix("755", 8).unwrap()`
How do I convert octal to decimal on Linux?	`echo $((8#755))`
How do I convert octal to decimal by hand?	`Multiply each digit by 8 raised to its position, counting from 0 on the right, then add. 755 = 7 x 64 + 5 x 8 + 5 x 1 = 448 + 40 + 5 = 493.`
What is the decimal value of octal 777?	`511. That is 7 x 64 + 7 x 8 + 7, the largest 3-digit octal number, and the chmod mode rwxrwxrwx.`
How do I read a chmod mode in decimal?	`Each octal digit is one permission group. 755 is 493 in decimal and 644 is 420. Programs such as os.chmod() in Python accept either form when written as 0o755 or 493.`
Why does a leading 0 mean octal in some languages?	`C, JavaScript (older sloppy mode), PHP and the shell treat 0755 as octal, so 0755 is 493 and not 755. Modern JavaScript uses the explicit 0o755 form.`
How do I convert signed octal to a negative decimal?	`Set Read as to Two's complement. In 8 bits, 377 is -1 and 200 is -128. In 16 bits, 177777 is -1 and 100000 is -32768.`
How do I convert an octal fraction to decimal?	`Divide each digit after the point by 8, 64 and so on. 0.4 is 4/8 = 0.5, and 56.3 is 46 + 3/8 = 46.375.`
Why do I get an invalid character error?	`Octal uses only the digits 0 to 7. Remove 8, 9, letters and stray symbols. A 0o prefix, spaces and underscores are ignored.`
How do I convert decimal back to octal?	`JavaScript: (493).toString(8). Python: format(493, 'o'). Result: 755.`