Ratings

In the United States, The 100 is shown on The CW. For ratings of The 100 airing in the United Kingdom, click here. To see how the users rated the episodes on IMDb, click here

Airdays

• Season One aired on Wednesdays 9PM following Arrow. It was part of the CW's midseason lineup.
• Season Two aired on Wednesdays 9PM following Arrow. It was the only season during which the show was part of the CW's fall lineup
• Season Three aired on Thursdays at 9PM following Legends of Tomorrow. It was part of the CW's midseason lineup.
• Season Four aired on Wednesdays at 9PM following Arrow. It was part of the CW's midseason lineup.
• Season Five aired on Tuesday nights at 9PM following The Flash for the first eight episodes. It airs on Tuesday nights at 8PM prior to The Outpost for the remaining five episodes of the season. It is part of the CW's midseason and summer lineups.

The morning after the episode airs, preliminary ratings (Nielsen ratings) are announced. Less than 24 hours after the episode aired, the final ratings are released and those are added instead of preliminary ratings.

Season One Ratings

The most watched episode in Season One was Pilot, and least watched was I Am Become Death. This season had an average of 1.85 million viewer per episode

No.	Episode	U.S. Viewers (in millions)	Difference	Adults 18-49 share	Source
1	Pilot	2.73	N/A	0.9	[1]
2	Earth Skills	2.27	0.46 ↓	0.7	[2]
3	Earth Kills	1.90	0.37 ↓	0.6	[3]
4	Murphy's Law	1.69	0.21 ↓	0.5	[4]
5	Twilight's Last Gleaming	1.80	0.21 ↑	0.5	[5]
6	His Sister's Keeper	1.97	0.17 ↑	0.6	[6]
7	Contents Under Pressure	1.88	0.09 ↓	0.6	[7]
8	Day Trip	1.64	0.24 ↓	0.6	[8]
9	Unity Day	1.73	0.09 ↑	0.6	[9]
10	I Am Become Death	1.46	0.27 ↓	0.5	[10]
11	The Calm	1.71	0.25 ↑	0.6	[11]
12	We Are Grounders (Part 1)	1.58	0.13 ↓	0.6	[12]
13	We Are Grounders (Part 2)	1.68	0.10 ↑	0.5	[13]

Season Two Ratings

The most watched episode in Season Two was Fog of War, and least watched was Rubicon. This season had an average of 1.54 million viewers.

No.	Episode	U.S. Viewers (in millions)	Difference	Adults 19-49 share	Source
1	The 48	1.54	0.14 ↓	0.5	[14]
2	Inclement Weather	1.48	0.06 ↓	0.5	[15]
3	Reapercussions	1.68	0.20 ↑	0.5	[16]
4	Many Happy Returns	1.75	0.07 ↑	0.5	[17]
5	Human Trials	1.64	0.11 ↓	0.6	[18]
6	Fog of War	1.86	0.18 ↑	0.6	[19]
7	Long Into an Abyss	1.62	0.24 ↓	0.6	[20]
8	Spacewalker	1.40	0.22 ↓	0.5	[21]
9	Remember Me	1.48	0.08 ↑	0.5	[22]
10	Survival of the Fittest	1.53	0.05 ↑	0.5	[23]
11	Coup de Grâce	1.51	0.02 ↓	0.5	[24]
12	Rubicon	1.36	0.15 ↓	0.5	[25]
13	Resurrection	1.42	0.06 ↑	0.5	[26]
14	Bodyguard of Lies	1.55	0.13 ↑	0.5	[27]
15	Blood Must Have Blood (Part 1)	1.49	0.06 ↓	0.5	[28]
16	Blood Must Have Blood (Part 2)	1.34	0.15 ↓	0.4	[29]

Season Three Ratings

The most watched episode in Season Three was Wanheda (Part 1), and least watched was Nevermore. This season had an average of 1.32 million viewers.

No.	Episode	U.S. Viewers (in millions)	Difference	Adults 19-49 share	Source
1	Wanheda (Part 1)	1.88	0.54 ↑	0.7	[30]
2	Wanheda (Part 2)	1.63	0.25↓	0.6	[31]
3	Ye Who Enter Here	1.57	0.06↓	0.6	[32]
4	Watch the Thrones	1.32	0.25↓	0.5	[33]
5	Hakeldama	1.36	0.04↑	0.5	[34]
6	Bitter Harvest	1.41	0.05↑	0.6	[35]
7	Thirteen	1.39	0.02↓	0.5	[36]
8	Terms and Conditions	1.20	0.19↓	0.4	[37]
9	Stealing Fire	1.23	0.03↑	0.4	[38]
10	Fallen	1.13	0.10↓	0.4	[39]
11	Nevermore	1.08	0.05↓	0.4	[40]
12	Demons	1.15	0.07↑	0.4	[41]
13	Join or Die	1.27	0.12↑	0.4	[42]
14	Red Sky at Morning	1.13	0.14↓	0.4	[43]
15	Perverse Instantiation (Part 1)	1.17	0.04↑	0.4	[44]
16	Perverse Instantiation (Part 2)	1.29	0.12↑	0.5	[45]

Season Four Ratings

The most watched episode in Season Four was Echoes, and least watched was DNR. This season had an average of 0.95 million viewers per episode.

No.	Episode	U.S. Viewers (in millions)	Difference	Adults 19-49 share	Source
1	Echoes	1.21	0.08↓	0.4	[46]
2	Heavy Lies the Crown	1.01	0.20↓	0.4	[47]
3	The Four Horsemen	1.05	0.04↑	0.4	[48]
4	A Lie Guarded	1.00	0.05↓	0.4	[49]
5	The Tinder Box	1.02	0.02↑	0.4	[50]
6	We Will Rise	0.98	0.04↓	0.3	[51]
7	Gimme Shelter	0.90	0.08↓	0.3	[52]
8	God Complex	0.97	0.07↑	0.3	[53]
9	DNR	0.81	0.16↓	0.3	[54]
10	Die All, Die Merrily	0.85	0.04↑	0.3	[55]
11	The Other Side	0.86	0.01↑	0.3	[56]
12	The Chosen	0.83	0.03↓	0.3	[57]
13	Praimfaya	0.91	0.08↑	0.3	[58]

Season Five Ratings

The most watched episode in Season Five was TBA, and least watched was TBA. This season had an average of TBA million viewers per episode.

No.	Episode	U.S. Viewers (in millions)	Difference	Adults 19-49 share	Source
1	Eden	1.43	↑0.52	0.4	[59]
2	Red Queen	1.02	↓0.41	0.3	[60]
3	Sleeping Giants	1.08	↑0.06	0.4	[61]
4	Pandora's Box	1.07	↓0.01	0.3	[62]
5	Shifting Sands	0.94	↓0.13	0.3	[63]
6	Exit Wounds	0.92	↓0.02	0.3	[64]
7	Acceptable Losses	0.83	↓0.09	0.3	[65]
8	How We Get to Peace	0.73	↓0.10	0.2	[66]
9	Sic Semper Tyrannis	0.89	↑0.16	0.3	[67]
10	The Warriors Will	0.86	↓0.03	0.2	[68]
11	The Dark Year	0.85	↓0.01	0.3	[69]
12	Damocles (Part 1)	0.88	↑0.03	0.3	[70]
13	Damocles (Part 2)	0.99	↑0.11	0.3	[71]