Hope this helps - Unfortunately I couldn't find a calculator.

HP Integrity rx7640 Server - specifications

Power requirements:
Typical power dissipation: : 2,030 VA (Maximum configuration)
Input current: 10.2 A @ 200 VAC
Electromagnetic interference: UL listed, CUL certified, compliant with EN 60950
Safety: Complies with FCC rules and regulations, Part 15, as a Class A Digital
Device; Manufacturer’s declaration to EN55022 Level A, VCCI registered, Class I, Korea RLL
Power line LF emissions Europe: EN 61000-3-2;
Europe: EN Input current: 61000-3-3 AC
input power: AC Input power: 200–240 V, 50–60 Hz