$25,000 is not a meaningful number for federal income tax liability. If one is single, the standard deduction and exemption write-off just $10,350. Taxes kick in after that, and before that if one didn't have FICA taxes withheld or is being claimed as a dependent.
So, if one had a "simple" return with exactly $25,000 in wages, there would be taxable income of $14,560.
The tax on that would be in the vicinity of $900.
Your tax return may also include self-employment taxes, penalties and other taxes in addition to regular income tax.
A gross salary of $25,000 is not exempt from tax, as it is not below $10,350.