Get your taxes done using TurboTax

Yes, @dyons when preparing your return using TurboTax Self-Employed, you can check the box to allow TurboTax to calculate your maximum 401(k) contribution. 

Individual 401(k) plans for the self-employed (also called solo 401k or solo-K plans) are entered in the Other Business Situations section of Income & Expenses in TurboTax. You can quickly jump to this section while preparing your return if you click on the search box at the top right of the page and type "self employed 401k" then click on the first result, which is jump to self employed 401k. As you work through this section, you will see a page titled, "Individual and Roth 401(k) plans" click on the box to "maximize contributions to 401(k)" and continue to have TurboTax calculate it for you. (See pic below.)

For more information, take a look at: Can the Self-Employed Have a 401(k)?