Battery Runtime Calculator
Use our free battery runtime calculator to estimate backup hours for APC UPS, CyberPower, and standalone battery banks. This UPS battery runtime calculator supports 12V lead-acid, LiFePO4 lithium, and custom loads in watts — instant results with no sign-up required.
Battery Runtime Calculator
UPS · APC · CyberPowerBattery Specifications
Load & Battery Type
Sum of all devices connected to the battery or UPS
DoD multiplier: 0.5 (50% usable)
Formula: Runtime = (Ah × V × DoD) ÷ Watts
Backup Runtime Results
Enter battery capacity, voltage, and load to estimate runtime
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What Is a Battery Runtime Calculator?
A battery runtime calculator estimates how long your battery or UPS system will power connected devices before depletion. Whether you need an APC UPS runtime calculator, a CyberPower runtime calculator, or a general UPS run time calculator — the math is the same: convert amp-hours and voltage to watt-hours, apply depth of discharge, then divide by your total load in watts.
Our tool works as an APC runtime calculator, CyberPower UPS runtime calculator, and lithium battery run time calculator in one interface. Enter your specs and get backup time in hours and minutes instantly.
How to Calculate Battery Runtime Manually
Follow these steps to manually calculate backup time using the Capacity × Voltage × DoD formula — the same logic behind every battery runtime calculator watts tool:
- 1Calculate Total Watt-Hours
Total Wh = Capacity (Ah) × Voltage (V). Example: 100 Ah × 12V = 1,200 Wh.
- 2Apply Depth of Discharge
Usable Wh = Total Wh × DoD. Lead-acid: × 0.50. LiFePO4: × 0.90. Lithium-ion: × 0.80.
- 3Divide by Power Load
Runtime (hours) = Usable Wh ÷ Load (W). Example: 600 Wh ÷ 200W = 3 hours.
Master Formula
Runtime (hrs) = (Ah × V × DoD) ÷ Watts12V Lead-Acid vs. LiFePO4 Runtime Comparison
A standard 12v battery run time calculator using lead-acid chemistry applies only 50% depth of discharge — draining further damages the battery. An advanced lifepo4 battery run time calculator unlocks 90% DoD, delivering dramatically longer backup from identical Ah and voltage ratings.
| Battery Type | DoD | 100Ah × 12V Usable Wh | Runtime @ 200W |
|---|---|---|---|
| Lead-Acid / AGM (50% DoD) | 50% | 600 Wh | 3 Hours 0 Minutes |
| LiFePO4 / Lithium Iron Phosphate (90% DoD) | 90% | 1080 Wh | 5 Hours 24 Minutes |
| Custom Lithium-Ion (80% DoD) | 80% | 960 Wh | 4 Hours 48 Minutes |
Key takeaway: A 100Ah LiFePO4 12V battery delivers 1,080 Wh usable vs. only 600 Wh from lead-acid — nearly 80% more runtime at the same load. This is why lithium UPS upgrades are popular for home labs and network closets.
Common Device Backup Duration Reference
Estimated backup times using a 100Ah × 12V LiFePO4 battery (90% DoD = 1,080 Wh usable) — compare how load watts dramatically affect your UPS battery runtime calculator output:
| Device / Load | Power Draw | Est. Runtime (100Ah LiFePO4) | Notes |
|---|---|---|---|
| WiFi Router | 15 W | 72 Hours 0 Minutes | Typical home mesh or cable modem router |
| Laptop Charger | 65 W | 16 Hours 36 Minutes | Single laptop on AC adapter |
| Refrigerator (Mini) | 150 W | 7 Hours 12 Minutes | Compact fridge — surge higher on compressor start |
| Desktop PC | 200 W | 5 Hours 24 Minutes | Office workstation, no dedicated GPU |
| Gaming PC | 400 W | 2 Hours 42 Minutes | High-end GPU + CPU under load |
| Window AC Unit | 900 W | 1 Hour 12 Minutes | Small room air conditioner — high surge on startup |
A WiFi Router at 15W runs ~72 hours on this bank, while a Gaming PC at 400W lasts only ~2.7 hours — illustrating why accurate wattage input is critical for any battery runtime calculator.
Battery Runtime Calculation Example
Sample: APC-Style 12V 100Ah AGM Battery, 200W Load
- • Capacity: 100 Ah
- • Voltage: 12V
- • Battery: Lead-Acid / AGM (50% DoD)
- • Load: 200 Watts
Total Wh = 100 × 12 = 1,200 WhUsable Wh = 1,200 × 0.50 = 600 WhResult: 3 Hours 0 Minutes
600 Wh ÷ 200W = 3.0 hours of backup runtime
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