Power Bank Runtime Calculator
Estimate how many full phone charges a power bank provides.
About the Power Bank Runtime Calculator
The Power Bank Runtime Calculator is a free, private tool that runs entirely in your browser — your inputs never leave your device, and the answer appears the instant you enter them.
Battery capacity, charging time and backup duration are the numbers behind every phone, UPS and solar installation in Pakistan. This Power Bank Runtime Calculator computes one of these battery figures so your power planning is based on real numbers.
The calculation uses the standard relationships between battery capacity (Ah or Wh), device load, and time — the same math used to size UPS and solar batteries.
With load-shedding still part of life in many areas, battery backup planning matters: how long will a UPS keep a fan and lights running, or how big a battery does a solar system need for overnight power? This calculator answers those questions.
Remember that batteries should not be discharged fully — lead-acid batteries last far longer when kept above 50% charge. Factor that reserve into your planning.
For the most accurate outcome from the Power Bank Runtime Calculator, keep the editable rates and defaults up to date with current figures before reading the result.
How to use the battery calculator
- 1
Enter the battery capacity and the load it powers.
- 2
Adjust the efficiency or discharge limit if the tool asks.
- 3
Read the backup time or required capacity, updated live.
Frequently Asked Questions
Why doesn't a 20,000 mAh power bank charge a 5,000 mAh phone 4 times?
Voltage conversion and internal losses waste ~15% of the power bank's capacity, so a 20,000 mAh bank delivers roughly 17,000 mAh — about 3.4 charges.
How long will a UPS battery last?
Divide the battery's usable capacity (in Wh) by the load (in watts). A 150 Ah, 12 V battery holds 1,800 Wh; powering 200 W of fans and lights gives roughly 7–8 hours of backup at normal discharge.
Should I discharge my battery fully?
No — deep discharge damages lead-acid batteries and cuts their life sharply. Keep discharge above 50% for lead-acid; lithium batteries tolerate deeper discharge but still last longer with a reserve.