| Document and Entity Information | Aug. 08, 2022 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Aug. 08, 2022 |
| Entity Registrant Name | PHX MINERALS INC. |
| Entity Central Index Key | 0000315131 |
| Entity Emerging Growth Company | false |
| Entity File Number | 001-31759 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 73-1055775 |
| Entity Address, Address Line One | 1320 South University Drive |
| Entity Address, Address Line Two | Suite 720 |
| Entity Address, City or Town | Fort Worth |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 76107 |
| City Area Code | 405 |
| Local Phone Number | 948-1560 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of each class | Common Stock, $0.01666 par value |
| Trading Symbol(s) | PHX |
| Name of each exchange on which registered | NYSE |
