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: 11 August 2026Sources: Li-ion cell voltage, USB output voltage, independent efficiency tests, published phone specs, IATA/DGCA
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
Airline cabin limit ≈ 27,000mAh at 3.7V
IATA / DGCA lithium rule
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 and flight hassle.

The airline rule (watt-hours, not mAh): India's DGCA and IATA cap cabin power banks at 100 Wh without approval — about 27,000mAh at 3.7 V. A 20,000mAh bank is ~74 Wh (fine); a 27,000mAh bank sits right at the ~100 Wh line; a 30,000mAh bank (~111 Wh) needs airline approval. Power banks must fly in carry-on, never checked baggage — and airlines and India's DGCA have tightened in-flight use and quantity rules recently, 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?
Airlines limit power banks by watt-hours, not mAh. The cabin limit under IATA and India’s DGCA rules is 100Wh without airline approval, which at the 3.7V cell voltage is about 27,000mAh. So a 20,000mAh bank (≈74Wh) is fine, a 27,000mAh bank is right at the 100Wh line, and banks above that (for example 30,000mAh ≈ 111Wh) need airline approval or are not allowed in the cabin. Power banks must always travel in carry-on, never checked baggage. Airlines and India’s DGCA have also tightened in-flight use and quantity rules recently, 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 the practical maximum before you hit the airline limit. Above 20,000mAh you mostly add weight and flight hassle; 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 Dangerous Goods Regulations and India DGCA rules: 100 Wh cabin limit without approval, 100–160 Wh with approval, power banks in carry-on only.

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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