Your deduction for charitable gifts is not tied to a set percentage of your income.  The deduction for charitable gifts is one of itemized deductions you claim on your tax return.  Unless your charitable gifts and other itemized deductions exceed your standard deduction, you'll receive the standard deduction.  For example, in 2016 a single taxpayer has a standard deduction of $6,300.  If your only itemized deduction for the year is $3,984 in charitable gifts, you'll receive the larger standard deduction, with no deduction for your donations.

You can follow this link to read more about standard and itemized deduction.  https://turbotax.intuit.com/tax-tools/tax-tips/Tax-Deductions-and-Credits/What-Are-Standard-Tax-Dedu...