UPS Size & Runtime Calculator
Estimate W and VA rating floors plus a shutdown-runtime energy target, then verify the exact load on a manufacturer runtime curve.
Runtime is approximate
Nameplate VA does not determine battery runtime. Use How to Size a UPS for a NAS and UPS Watts, VA, Power Factor, and Runtime before purchase.
Decision guide
Use UPS Size & Runtime Calculator with confidence
This guide explains the UPS load floor decision behind UPS Size & Runtime Calculator, the evidence worth collecting for watts, VA, and runtime, and the boundaries of its UPS specification floor. Work through UPS Size & Runtime Calculator after a first run, then revise manufacturer battery curve until the output reflects realistic conditions rather than convenience.
What this tool helps you decide
Estimate UPS watt and VA floors, headroom, energy, and shutdown-runtime target for a NAS system. The UPS Size & Runtime Calculator turns that UPS load floor question into a vendor-neutral UPS specification floor, not a product endorsement. Use UPS Size & Runtime Calculator before requesting quotes, because manufacturer battery curve can change the sensible watts, VA, and runtime choice. Keep that scope visible whenever the UPS specification floor is compared with alternatives.
Before you start
Measure connected-device watts, add startup or growth headroom, enter power factor, desired runtime minutes, and UPS efficiency. Include NAS, switches, and any equipment required for a clean shutdown. For UPS Size & Runtime Calculator, write the UPS load floor assumption beside every saved result. That UPS specification floor record lets another person reproduce the watts, VA, and runtime scenario, challenge manufacturer battery curve, and rerun UPS Size & Runtime Calculator after conditions change. Test one conservative UPS load floor case and one demanding case, then compare their UPS specification floor range.
How the calculation or recommendation works
Headroom increases connected watts; dividing watts by power factor estimates VA. Runtime energy is headroom watts times hours divided by efficiency. The displayed recommendation rounds VA and watt floors upward. The UPS Size & Runtime Calculator keeps UPS load floor arithmetic transparent, allowing the UPS specification floor to be checked without a vendor account. In UPS Size & Runtime Calculator, follow every watts, VA, and runtime unit shown by UPS Size & Runtime Calculator. Decimal TB and TiB answer capacity questions. Keep every UPS Size & Runtime Calculator input in its displayed unit; preserve those UPS Size & Runtime Calculator labels when sharing or checking the result. Round the UPS specification floor upward only after reviewing the unrounded UPS Size & Runtime Calculator result.
How to interpret the results
Both VA and watt ratings must be satisfied. Energy is an approximate battery requirement, not a catalog match. Runtime should cover outage detection, orderly job completion, and automated shutdown rather than prolonged operation. Read the UPS Size & Runtime Calculator summary with its UPS load floor metrics. Use the UPS Size & Runtime Calculator table and caution note to examine the complete watts, VA, and runtime tradeoff. Save manufacturer battery curve inputs with the result, compare scenarios under the same UPS load floor definition, and investigate conflicting UPS specification floor output before acting.
Worked example
A 120 W load with 30% headroom becomes 156 W. At 0.7 power factor the floor is about 223 VA, rounded to 250 VA, while fifteen minutes at 80% efficiency needs roughly 49 Wh. This UPS Size & Runtime Calculator example demonstrates the UPS load floor path, not a universal default. Change manufacturer battery curve one input at a time, observe which watts, VA, and runtime output moves, and note whether the UPS specification floor remains stable. Sensitivity around UPS load floor is more useful than copying another person’s final number.
Assumptions and limitations
Battery age, temperature, inverter curve, load shape, startup surge, outlet grouping, power quality, and vendor runtime behavior are not modeled. Nameplate VA alone does not prove the required runtime. The UPS Size & Runtime Calculator is a planning aid for watts, VA, and runtime in UPS Size & Runtime Calculator. Treat the UPS load floor assumptions as boundaries: the UPS specification floor supports UPS load floor planning only. It does not certify an implementation of UPS Size & Runtime Calculator, guarantee recovery, or provide financial advice. Recheck manufacturer battery curve, documentation relevant to UPS Size & Runtime Calculator, and operating requirements before purchasing for UPS Size & Runtime Calculator, migrating data, or approving a policy.
Next steps
Compare the watt and VA floors with the manufacturer load/runtime chart, include shutdown communication support, test an actual power-loss sequence, and schedule battery inspection and replacement. Continue from UPS Size & Runtime Calculator to the How to Size a UPS for a NAS, then carry the UPS Size & Runtime Calculator finding into another cost power tool for the next UPS Size & Runtime Calculator watts, VA, and runtime decision. Keep the UPS Size & Runtime Calculator UPS specification floor with its assumptions. Record the decision date for UPS Size & Runtime Calculator; assign a reviewer and a dated measurement checkpoint.