Enter your due date or last period once, and see your week & wheel, your pregnancy month, and your weight gain range together — no re-entering the same date four times.
No — the week, wheel and pregnancy-month sections work from your due date or last period alone. Weight and height are only needed for the weight gain range, since that's based on your pre-pregnancy BMI.
It's the same underlying math as the Due Date Calculator, Pregnancy Wheel, Weeks to Months and Weight Gain calculators — this page just runs all of them from one shared date so you don't have to re-enter it four times. Each section links through to its full calculator for more detail.
The week, wheel and month sections use the same 280-day estimate either way. For twin-specific weight gain guidelines, use the "Open Weight Gain Calculator" link and check the twins option there.