UPS Battery Backup Size Calculator
Calculate the right UPS (Uninterruptible Power Supply) size for your devices.
Enter wattage to get a recommended VA rating.
Recommended UPS Size
UPS sizing converts the total watts of your connected devices to the required VA (Volt-Ampere) rating using a power factor.
Required VA = Total Watts / Power Factor
The standard power factor for computing equipment is 0.6–0.8. We use 0.6 for a safe margin.
Common device power consumption:
| Device | Watts |
|---|---|
| Desktop computer | 200–500 |
| Monitor (24") | 30–60 |
| Monitor (27"+) | 50–80 |
| Laptop (charging) | 45–90 |
| Router/modem | 10–20 |
| External hard drive | 10–30 |
| Inkjet printer | 30–50 |
| Laser printer | 300–600 (peak) |
| Gaming PC | 400–800 |
| NAS (2-bay) | 20–40 |
UPS sizing guide:
| VA Rating | Typical Use |
|---|---|
| 350–500 VA | Modem, router |
| 750–1000 VA | Basic PC + monitor |
| 1500 VA | Gaming PC or PC + peripherals |
| 2200 VA | Workstation + multiple monitors |
| 3000+ VA | Server or multiple workstations |
Tips:
- Never load a UPS above 80% of its rated capacity
- Higher VA rating = longer runtime during a power outage
- Line-interactive UPS is best for home/office use
- Online/double-conversion UPS is best for servers