| Document and Entity Information | Feb. 02, 2022 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Feb. 2, 2022 |
| Entity Registrant Name | FAST RADIUS, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-40032 |
| Entity Tax Identification Number | 85-3692788 |
| Entity Address, Address Line One | 113 N. May Street |
| Entity Address, City or Town | Chicago |
| Entity Address, State or Province | IL |
| Entity Address, Postal Zip Code | 60607 |
| City Area Code | 888 |
| Local Phone Number | 787-1629 |
| Entity Information, Former Legal or Registered Name | ECP Environmental Growth Opportunities Corp. |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Amendment Flag | false |
| Entity Central Index Key | 0001832351 |
| Former Address [Member] | |
| Document Information [Line Items] | |
| Entity Address, Address Line One | 40 Beechwood Road |
| Entity Address, City or Town | Summit |
| Entity Address, State or Province | NJ |
| Entity Address, Postal Zip Code | 07901 |
| Common stock, par value $0.0001 per share [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common stock, par value $0.0001 per share |
| Trading Symbol | FSRD |
| Security Exchange Name | NASDAQ |
| Warrants [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Warrants, each whole warrant exercisable for one share of common stock at an exercise price of $11.50 per share |
| Trading Symbol | FSRDW |
| Security Exchange Name | NASDAQ |
