Claiming someone as a dependent is not relevant when completing a W-4. The W-4 that you give to your employer is for the amount of taxes that will be withheld from your wages.
Use this TurboTax W-4 calculator - https://turbotax.intuit.com/tax-tools/calculators/w4/
Note - When you are married you should be filing your tax return as Married Filing Jointly. A spouse cannot claim you as a dependent. If you have children and filing as MFJ, then both of you are claiming them as dependents when you file your tax return.