As fanfare mentioned above, don't forget that your estimated taxes would include both income tax and self-employment tax.
Also be aware that if you live in an income tax state, you may have to pay quarterly state estimated taxes as well.
Once you know the amount you want to pay each quarter, if you prefer to pay electronically, there are a couple of options to make Federal estimated payments that require no paperwork and no mail. By paying electronically you don't have to mail a Form 1040-ES voucher and check.
One easy way is to make 1040-ES quarterly payments by using IRS Direct Pay electronically, and nothing has to be filled out and mailed.
https://www.irs.gov/payments
There is no fee to pay electronically at the IRS Direct Pay site if you choose to have it taken directly out of your bank account (ACH electronic withdrawal.)
There is a service fee for paying by credit/debit card, however. (NOTE: If paying by credit card, there can be a hefty service fee.)
If you decide to make a payment there out of your bank account, for "Reason for Payment" choose "Estimated tax". For "Apply Payment To" choose "1040-ES". Then choose the tax year you're paying.
After paying, print out a confirmation for your records.
The advantage of IRS Direct Pay is that it doesn't require an initial pre-enrollment, unlike EFTPS which I'll explain in the next paragraph.
While you can use IRS Direct Pay each quarter, if desired, if you think you are going to be making quarterly payments for a long time into the future, then you may want to consider opening a free account at the US Treasury's EFTPS website (Electronic Federal Tax Payment System.) You can even schedule quarterly payments in advance and make other types of Federal tax payments, such as a balance due on your Form 1040, etc. For first time use, you have to set it up in advance with your banking info, and they send you a PIN in postal mail. Once set up, you can then make online payments there at the EFTPS website, or payments can be made by phone with the PIN. For more info on EFTPS, there is an extensive FAQ page in the left menu column at this link:
https://www.eftps.gov/eftps/
