UPS runtime calculator

Input
Options
Result

UPS runtime calculator

Estimate backup time, compare battery energy and check continuous and starting-power limits.

Calculator settings

Start with a load

Devices and target runtime

Load power

Starting peak

Target runtime

min

Main battery configuration A

Config A voltage

Config A capacity

Config A batteries

UPS power limits

UPS rating

UPS continuous rating

Use the manufacturer watt rating; 0 means unknown, not unlimited.UPS surge rating

Power factor

Efficiency and battery condition

UPS efficiency

Battery aging factor

Usable depth of discharge

Optional battery comparisons B and C

Config B voltage

Config B capacity

Config B batteries

Config C voltage

Config C capacity

Config C batteries

An estimate, not a wiring recommendationBattery energy is voltage × Ah × count; voltage is per battery, not the whole string. Real runtime also depends on discharge current, chemistry and UPS idle consumption. Compare with the manufacturer runtime curve. Do not change battery voltage, wiring or external-battery count unless the UPS supports it. Zero B/C battery count excludes that comparison.

Result

Main runtime

18 min

Best runtime

98 min

Configuration C

Estimated VA load

500 VA

UPS rating: 1,000 VA

Required battery

368 Wh

31 Ah @ 12 V

Peak power reserve

27.78%

650 / 900 W

Target runtime: 30 min
Required usable energy: 175 Wh
Main usable energy: 103 Wh
Main nominal energy: 216 Wh
Starting peak: 650 W
UPS surge rating: 900 W
Efficiency / aging / DoD: 85% / 80% / 70%
Formula: runtime = battery V x Ah x count x efficiency x aging x DoD / load W
Energy-equivalent battery count for target: 4

Target runtime	30 min
Required usable energy	175 Wh
Main usable energy	103 Wh
Main nominal energy	216 Wh
Starting peak	650 W
UPS surge rating	900 W
Efficiency / aging / DoD	85% / 80% / 70%
Formula	runtime = battery V x Ah x count x efficiency x aging x DoD / load W
Energy-equivalent battery count for target	4

Configuration comparison

Configuration: Configuration A
Battery: 2 x 12 V 9 Ah
Nominal energy: 216 Wh
Usable energy: 103 Wh
Runtime: 18 min
Target: Below target
Max load for target: 206 W

Configuration: Configuration B
Battery: 2 x 12 V 18 Ah
Nominal energy: 432 Wh
Usable energy: 206 Wh
Runtime: 35 min
Target: OK
Max load for target: 411 W

Configuration: Configuration C
Battery: 2 x 12 V 50 Ah
Nominal energy: 1,200 Wh
Usable energy: 571 Wh
Runtime: 98 min
Target: OK
Max load for target: 1,142 W

Configuration	Battery	Nominal energy	Usable energy	Runtime	Target	Max load for target
Configuration A	2 x 12 V 9 Ah	216 Wh	103 Wh	18 min	Below target	206 W
Configuration B	2 x 12 V 18 Ah	432 Wh	206 Wh	35 min	OK	411 W
Configuration C	2 x 12 V 50 Ah	1,200 Wh	571 Wh	98 min	OK	1,142 W

Main configuration does not reach the target runtime.

UPS battery runtime and capacity calculator

The calculator estimates usable battery energy, expected runtime, VA load and the battery capacity needed for a target backup time.

Use the comparison table to check several battery configurations side by side before selecting a UPS or external battery pack.

Quick start

Estimate battery backup and check UPS power limits.

Enter device load and the main battery configuration
Check UPS watt and VA ratings and optional comparisons
Calculate and compare with the manufacturer runtime curve

✓ Use the calculator to turn input values into a clear, repeatable result.

✓ Keep units and assumptions visible so the calculation can be checked later.

✓ Copy the result or key numbers for reports, messages or spreadsheets.

✓ Reset to defaults when you want to compare another scenario from a clean state.

✓ Calculators run in the browser and are useful for quick estimates before formal checks.

✓ For finance, health, engineering or legal decisions, verify important results with a specialist or official source.

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