How Many Charges Does a Power Bank Really Give? (India 2026)

The mAh on a power bank is measured inside its cells at 3.7 volts — but your phone charges over USB at 5 volts. That step-up, plus normal conversion and cable losses, means only about 65%of the number on the box ever reaches your phone. Here is the real usable capacity, and the honest charge count, for every common power-bank size across popular India phones — computed from the physics, not the marketing.

Last updated: 8 October 2026Sources: Li-ion cell voltage, USB output voltage, independent efficiency tests, published phone specs, IATA
In short: a power bank delivers roughly 65% of its rated mAh to your phone. A 10,000mAh bank gives about 6,500mAh usable — about 1.9 charges of an iPhone 15, or just 1.3 charges of a typical 5,000mAh Android. A 20,000mAh bank gives about 3.9 iPhone or 2.6 Android charges — not the 5–6 the number implies. And a 5,000mAhbank can't fully charge a modern 5,000mAh phone even once. Buy for real charges, not headline mAh.

Key Numbers at a Glance

~65%
Of the rated mAh actually reaches your phone
typically 60–70%; we use 65%
1.3×
Charges a 10,000mAh bank gives a typical 5,000mAh Android
~6,500mAh usable
3.9×
iPhone 15 charges from a 20,000mAh bank — not the ~6 implied
~13,000mAh usable
0.65×
A 5,000mAh bank can’t fully charge a 5,000mAh phone
~3,250mAh usable
100 Wh
Per power bank in IATA’s guidance ≈ 27,000mAh at 3.7V
IATA 2026 passenger guidance
3.7V vs 5V
The whole reason: rated at cell voltage, delivered at USB voltage
physics, not marketing

Use this data

The full table as a CSV — rated capacity, usable output, watt-hours, and real charges for every phone. Free to reuse with attribution (CC BY 4.0).

How to cite: PakkaPick, “How Many Charges Does a Power Bank Really Give? (India 2026),” pakkapick.in/power-bank-real-charges-india-2026 — CC BY 4.0

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Why the mAh number is not the charges you get

A power bank's rated mAh is the capacity of the lithium cells inside, measured at their nominal voltage of 3.7 V. Your phone charges over USB at 5 V. Because energy(watt-hours) is what's conserved — not mAh — converting 3.7 V up to 5 V already drops the deliverable mAh to about 74% (3.7 ÷ 5).

On top of that, the boost converter that does the stepping-up, plus the cable and heat, lose roughly another 10–15%. Multiply the two and a good-quality bank delivers about 65% of its rated capacity to your phone; cheaper banks, fast-charging at higher voltages, cold weather and worn cables push it lower. So the honest formula is:

usable mAh at your phone  ≈  rated mAh  ×  0.65
charges of a phone  =  usable mAh  ÷  that phone's battery mAh

The 65% figure is a fair central estimate for a good bank on a standard 5 V cable; independent tests and manufacturer statements (including Anker's own) put real-world delivery in the 60–70% range. It is an efficiency estimate, not a fixed constant — your exact result varies with the bank, cable, output mode and temperature. Note that watt-hours (energy), not mAh, is the conserved quantity, so the charge counts below hold whether your phone charges at 5 V, 9 V or 12 V — a phone battery is also about 3.7 V, so the energy steps back down.

Real usable charges by capacity and phone

At ~65% delivery, here is what each common power-bank size actually gives the phones people buy in India. “Usable” is the mAh that reaches the phone; the charge columns are usable mAh divided by each phone's battery.

Usable output and full phone charges by power-bank capacity, at ~65% real-world efficiency.
Rated capacityUsable (≈65%)EnergyiPhone 15
3,349mAh		Galaxy S24
4,000mAh		OnePlus 12
5,400mAh		Typical 5,000mAh Android
5,000mAh
5,000mAh3,250mAh19 Wh1.0×0.8×0.6×0.7×
10,000mAh6,500mAh37 Wh1.9×1.6×1.2×1.3×
20,000mAh13,000mAh74 Wh3.9×3.3×2.4×2.6×
27,000mAh17,550mAh100 Wh5.2×4.4×3.3×3.5×
The one that surprises people: a 5,000mAh power bank delivers only ~3,250mAh — it cannot fully charge a modern 5,000mAh phone even once (0.65×), and gives an iPhone 15 just 0.97×. Treat 5,000mAh banks as a top-up, not a spare battery.

Phone battery capacities from manufacturer specs and regulatory filings (Apple does not publish iPhone mAh; the iPhone 15's 3,349mAh is from regulatory filings, as reported by GSMArena). Charge counts assume the bank starts full and ignore any charge already in the phone; real sessions vary. Numbers rounded to one decimal.

What capacity should you actually buy?

10,000mAh — the everyday sweet spot

About 1.9 iPhone or 1.3 Android charges, but light and pocketable. The right pick for a daily top-up in a bag. Delivers ~6,500mAh.

20,000mAh — the practical maximum

About 3.9 iPhone or 2.6 Android charges (~13,000mAh), and still under the airline limit. Best for travel and charging two devices. Above this you mostly add weight.

IATA's guidance (watt-hours, not mAh):IATA's guidance for passengers, revised for the 2026 regulations, says each passenger is limited to two power banks of up to 100 Wh each — about 27,000mAhat 3.7 V — in carry-on baggage only, and lists power banks above 100 Wh as forbidden (ICAO's rules provide for 100–160 Wh with the airline's approval). A 20,000mAh bank is ~74 Wh (within the limit); a 27,000mAh bank sits right at the ~100 Wh line; a 30,000mAh bank (~111 Wh) is over it. The guidance also says power banks must not be recharged from the aircraft's power supply. Airlines may set stricter rules, so check your airline's current policy before you fly.

Frequently Asked Questions

Why does a 10,000mAh power bank not charge my phone 2–3 times?
Because the 10,000mAh is measured inside the power bank at its lithium-cell voltage of 3.7V, while your phone charges over USB at 5V. Energy (watt-hours) is conserved, not mAh, so stepping 3.7V up to 5V already drops the deliverable capacity to about 74% — and the boost converter, cable and heat lose roughly another 10–15%. The real-world result is about 65% of the rated number reaching your phone. A 10,000mAh bank therefore delivers roughly 6,500mAh: about 1.9 charges of an iPhone 15 (3,349mAh) or only about 1.3 charges of a typical 5,000mAh Android.
How many times can a 20,000mAh power bank charge a phone?
A 20,000mAh bank delivers about 13,000mAh usable (≈65%). That is roughly 3.9 charges of an iPhone 15 (3,349mAh), about 3.3 charges of a 4,000mAh phone, or about 2.6 charges of a 5,000mAh Android — not the 5–6 the raw capacity implies.
Can a 5,000mAh power bank fully charge a phone?
Often not. A 5,000mAh bank delivers only about 3,250mAh to your phone, so it cannot fully charge a modern 5,000mAh Android even once (about 0.65 of a charge), and it gives an iPhone 15 just under one full charge. A 5,000mAh bank is a top-up, not a full spare battery.
What is the real efficiency of a power bank?
Reputable manufacturers and independent teardown tests put real-world delivery at roughly 60–70% of the rated capacity, with about 65% a fair central figure for a good-quality bank charging over a standard cable. The two losses are unavoidable physics (3.7V cell → 5V USB output ≈ 74%) plus conversion and heat loss in the boost circuit and cable (another ~10–15%). Cheap banks, fast-charging at higher voltages, cold weather and a worn cable push efficiency lower.
What size power bank can I take on a flight in India?
The limit is set in watt-hours, not mAh. IATA’s guidance for passengers, revised for the 2026 regulations, says each passenger is limited to two lithium-ion power banks of up to 100Wh each, in carry-on baggage only, and lists power banks above 100Wh as forbidden (ICAO’s rules provide for 100–160Wh with the airline’s approval). At the 3.7V cell voltage, 100Wh is about 27,000mAh. So a 20,000mAh bank (≈74Wh) is within the limit, a 27,000mAh bank is right at the 100Wh line, and a 30,000mAh bank (≈111Wh) is over it. The guidance also says power banks must not be recharged from the aircraft’s power supply. Airlines may set stricter rules, so check your airline’s current policy before flying.
What capacity power bank should I actually buy in India?
For a day’s top-up in a bag, a 10,000mAh bank (about 1.3–1.9 real charges) is the light, pocketable sweet spot. For travel, heavy use, or charging two devices, a 20,000mAh bank (about 2.6–3.9 real charges) is well under the airline limit. Above 20,000mAh you mostly add weight; below 10,000mAh you get less than a full spare charge for most phones. Match the number to real charges, not the headline mAh.
Does fast charging change how many charges I get?
Fast charging (18W–100W USB-PD) does not add capacity — the watt-hours stored are fixed — but it can slightly lower efficiency because higher output voltages and higher currents produce more heat, so you may see a touch fewer charges than a slow 5V/2A output from the same bank. The trade-off is usually worth it for the speed; just don’t expect fast charging to give you extra charges.

Sources & Methodology

Usable output = rated capacity × 0.65. The 0.65 comes from the 3.7 V → 5 V voltage step (≈0.74) times a typical ~0.88 conversion/cable/heat efficiency. Charges = usable output ÷ the phone's published battery capacity. Energy (Wh) = rated mAh × 3.7 V ÷ 1,000, the figure airlines use.

  • Lithium-ion nominal cell voltage 3.7 V; USB output 5 V — the physical basis of the voltage step and the watt-hour conservation.
  • Real-world efficiency ~60–70% — independent power-bank capacity tests and reputable-manufacturer statements on usable-vs-rated output; ~65% used as the central figure.
  • Phone battery capacities — Samsung and OnePlus published specs (Galaxy S24 4,000mAh; OnePlus 12 5,400mAh); Apple does not publish iPhone mAh, so the iPhone 15's 3,349mAh is from regulatory filings via GSMArena; the 5,000mAh figure represents the most common India Android capacity.
  • Airline limit — IATA, Passengers Travelling with Lithium Batteries (revised for the 2026 regulations): a maximum of two power banks of up to 100 Wh each, in carry-on baggage only; power banks above 100 Wh are listed as forbidden (ICAO's rules provide for 100–160 Wh with the airline's approval).

Figures are estimates for guidance, not a guarantee: your exact result depends on the specific bank, cable, output mode (5 V vs fast-charge), temperature and battery age. This page contains no product prices.

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