| Cover | Dec. 15, 2021 |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Dec. 15, 2021 |
| Entity File Number | 001-38250 |
| Entity Registrant Name | FAT Brands Inc. |
| Entity Central Index Key | 0001705012 |
| Entity Tax Identification Number | 82-1302696 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 9720 Wilshire Blvd. |
| Entity Address, Address Line Two | Suite 500 |
| Entity Address, City or Town | Beverly Hills |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 90212 |
| City Area Code | (310) |
| Local Phone Number | 319-1850 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | true |
| Elected Not To Use the Extended Transition Period | true |
| Entity Information, Former Legal or Registered Name | Not Applicable |
| Class A Common Stock | |
| Title of 12(b) Security | Class A Common Stock |
| Trading Symbol | FAT |
| Security Exchange Name | NASDAQ |
| Class B Common Stock | |
| Title of 12(b) Security | Class B Common Stock |
| Trading Symbol | FATBB |
| Security Exchange Name | NASDAQ |
| Series B Cumulative Preferred Stock | |
| Title of 12(b) Security | Series B Cumulative Preferred Stock |
| Trading Symbol | FATBP |
| Security Exchange Name | NASDAQ |
| Warrants to purchase Common Stock | |
| Title of 12(b) Security | Warrants to purchase Common Stock |
| Trading Symbol | FATBW |
| Security Exchange Name | NASDAQ |
