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Power & UPS Tool

UPS Runtime Calculator

Estimate backup runtime for UPS systems using load, battery capacity, battery voltage, efficiency, usable capacity and reserve margin.

Updated: June 7, 2026Planning reference

Quick Answer

Estimate UPS runtime before relying on battery backup for infrastructure equipment.

Enter UPS load and battery data. The calculator estimates usable battery energy, VA load, runtime minutes and practical runtime band.

UPS Runtime

Runtime input

Enter UPS load and battery details. Runtime is estimated automatically for early planning.

Formula used

Runtime ≈ (Battery V × Ah × strings × usable capacity × efficiency × reserve factor) ÷ load W

Planning note

Runtime estimates depend heavily on battery condition, UPS model, discharge curve and temperature.

Formula / Method

What the calculator does

The calculator estimates raw battery energy, usable battery energy after efficiency and reserve margin, then divides usable watt-hours by connected load to estimate runtime.

Runtime ≈ usable Wh ÷ load W

Inputs

Required inputs

Use connected load, UPS power factor, battery voltage, battery Ah capacity, number of strings, UPS efficiency, usable battery percentage and reserve margin.

Uses

Where this helps

Useful for UPS sizing checks, server-room backup planning, rack power coordination, shutdown planning, generator transfer checks and infrastructure handover documentation.

FAQ

UPS runtime notes

Is this a final UPS runtime guarantee?

No. This is a planning estimate. Real UPS runtime depends on UPS model, battery age, temperature, discharge curve, load profile and manufacturer data.

Why use a reserve margin?

Reserve margin keeps planning conservative and avoids using the theoretical full battery capacity as if every battery were new and ideal.

Should I use watts or VA?

Runtime is estimated from watts. VA is shown as a planning reference using the selected power factor.

Learn More

Reference links

Project

Need help validating UPS backup runtime?

ITCOREOPS can support UPS planning, rack power coordination, PDU planning, infrastructure documentation and operational handover.

Open project formVisit ITCOREOPS →

Disclaimer

Planning reference only

This calculator provides a simplified planning estimate only. It does not replace UPS vendor runtime charts, battery discharge curves, qualified electrical review, site survey, local electrical regulations or final commissioning approval.

Workflow

UPS runtime should be checked before relying on battery backup.

Use this calculator before assigning equipment to a UPS, planning shutdown time, checking generator transfer assumptions or documenting backup-power requirements.

Use exact inputs ↑

Support

Need help with UPS or rack power planning?

For UPS planning, rack power, PDU layouts, structured cabling and operational infrastructure support, visit ITCOREOPS.

Visit ITCOREOPS →Email ITCOREOPS ✉

Feedback

Found a bug or export issue?

Report display problems, export issues or suggestions for improving this calculator.

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