The IRS has guidance on Determining the value of donated property in Publication 561
As an example, here is the guidance on used clothing: "Used clothing and other personal items are usually worth far less than the price you paid for them. Valuation of items of clothing does not lend itself to fixed formulas or methods.
The price that buyers of used items actually pay in used clothing stores, such as consignment or thrift shops, is an indication of the value.
You cannot take an income tax charitable contribution deduction for an item of clothing unless it is in good used condition or better. An item of clothing that is not in good used condition or better for which you claim an income tax charitable contribution deduction of more than $500 requires a qualified appraisal and a completed Form 8283. See Deduction over $500 for certain clothing or household items, later."
If making large donations of household goods and clothing, it would be be best to have those items evaluated prior to the donation for tax reporting purposes.
Some charitable organizations also have helpful guides on valuation of goods and clothing,
Please be sure to get receipts for large donations of items. Donations exceeding $500 of clothing do need report on Form 8283, while donations exceeding $5000 will require a qualified appraisal.
