For power banks, 10,000–20,000 mAh fits daily carry; choose 20,000–30,000 mAh for tablets, long days, or multi-device charging.
Shopping for a portable charger can feel confusing. Numbers on the box jump from 5,000 to 30,000 mAh, and wattage labels add one more layer. This guide trims the noise and gives you a clear way to pick the right capacity for your needs without wasting money or carrying a brick.
Good Power Bank Capacity: mAh Ranges That Make Sense
Capacity is the single figure most buyers care about. Below is a quick range-to-use map that reflects real-world expectations, not lab fantasy. It balances what a pack can deliver against weight, size, and the way phones and tablets sip power in bursts.
| mAh Range | Best Fit | Why It Works |
|---|---|---|
| 5,000–7,500 | Emergency top-ups | Tiny and light; pocket backup for a single phone boost. |
| 10,000 | Everyday carry | One to two phone refills; stays compact and travel-friendly. |
| 15,000–20,000 | Busy days & short trips | Two to three phone refills or one tablet charge. |
| 25,000–30,000 | Work travel & tablets | Enough for tablets, handheld consoles, or charging two phones repeatedly. |
| 30,000+ | Niche use | Bulky; consider only if you need many cycles without wall power. |
What mAh Actually Means (And Why Watt-Hours Matter)
Milliamp-hours (mAh) describes charge capacity, while watt-hours (Wh) captures stored energy. For a rough conversion, use Wh = (mAh × V) ÷ 1000. Most single-cell lithium packs inside portable chargers use about 3.6–3.7 V nominal. That means a 20,000 mAh pack at 3.7 V stores about 74 Wh; a 30,000 mAh pack stores about 111 Wh. Manufacturers often print both values on the label.
Why A 10,000 mAh Pack Doesn’t Give 10,000 mAh To Your Phone
Losses happen at every step. The pack re-regulates voltage from its cells to USB output, then your device regulates again to fill its battery. Heat and cable resistance add small losses. In independent tests, usable output often lands around 55–65% of the headline number, varying by charger design and the speeds you draw at. That’s why a 10,000 mAh unit usually refills a modern phone once and change, not twice.
Pick Your Capacity By Device And Day
Start with your device battery size and how long you’ll be away from a wall outlet. Many recent phones sit between 3,500 and 5,000 mAh; large flagships and gaming phones can climb above that. Tablets span a wide range from about 7,500 to 12,000 mAh, with bigger models above. The table below turns those realities into quick picks.
Fast Rules You Can Trust
- Daily carry, single phone: 10,000 mAh hits the sweet spot for size and one solid refill.
- Heavy phone use or two phones: 15,000–20,000 mAh keeps you covered through late nights.
- Tablet or handheld console: 20,000–30,000 mAh prevents mid-movie drop-offs.
- Weekend off-grid: 25,000–30,000 mAh or a compact power station measured in Wh.
Charging Speed, Ports, And Cables
Capacity is only half the story; charging speed controls how quickly power moves. USB-C Power Delivery (PD) raises charging ceilings, with the latest revision allowing up to 240 W when paired with certified EPR cables. That matters for laptops and fast-charging tablets. For phones, 18–30 W covers most needs; 45–65 W helps with larger tablets and many notebooks.
How To Read Wattage On The Box
Wattage equals volts times amps. A port marked 20 V / 3.25 A can deliver about 65 W. Many compact packs top out at 20–30 W, which is fine for phones. If you plan to top up a USB-C laptop, look for 45–65 W support and bring a cable rated for that level.
One Cable Detail That Trips Buyers
Not every USB-C cable supports high current. Standard cables carry up to 3 A; certified high-power EPR cables carry up to 5 A for 100–240 W charging. When a laptop refuses to charge fast, the cable is often the bottleneck.
Airline Limits: mAh To Wh And Safe Carry
If you fly, pay attention to watt-hour limits. Air carriers regulate spare lithium batteries by Wh, not mAh; see the IATA guidance. Packs up to 100 Wh can ride in carry-ons without special approval; 100–160 Wh usually needs airline permission; above that, leave it at home. A 20,000 mAh pack at 3.7 V sits under 100 Wh, so it clears the common threshold. Keep spare batteries out of checked bags.
How To Estimate Real-World Recharges
The headline number doesn’t equal delivered charge. A practical rule is to multiply the printed mAh by 0.6 to estimate what your device may receive. Then divide by your device battery size. It’s not exact, but it’s a good planning tool.
| Device Battery (mAh) | Estimated Refills With 10,000 mAh Pack | Estimated Refills With 20,000 mAh Pack |
|---|---|---|
| 3,000–3,500 | ~1.6–2.0 | ~3.2–4.0 |
| 4,000–4,500 | ~1.2–1.6 | ~2.4–3.2 |
| 5,000–5,500 | ~1.0–1.2 | ~2.0–2.4 |
| 7,500–10,000 (tablet) | ~0.6–1.0 | ~1.2–2.0 |
Port Mix: One Size Never Fits All
A balanced pack includes at least one USB-C PD port for fast in/out and one USB-A for legacy cables. Dual USB-C is handy if you juggle a phone and a laptop. If you want pass-through charging (powering a device while the pack itself charges), check the spec sheet; not every model supports it.
Size, Weight, And Build Cues
Higher mAh increases mass. A slim 10,000 mAh unit can weigh around 180–220 g; many 20,000 mAh packs land near 350–450 g, with 30,000 mAh rising past 550 g. Look for rounded edges, grippy sides, and a clear display for percentage and wattage. A real power button helps avoid phantom drains in a bag.
If you carry a small bag, compare dimensions, not just grams. Two packs with the same rating can feel different in hand because shape, grip texture, and port placement change how they ride in a pocket or sling.
Safety Features That Matter
Pick models with protection for over-current, over-voltage, and temperature. Reputable makers publish compliance to standards and carry proper markings. Avoid no-name packs that skip safety notes, ship without a manual, or disguise the true capacity.
Quick Picks By Scenario
Commute And Coffee Runs
Carry a 10,000 mAh slab. It stays pocketable, refills a phone once, and pairs well with a short USB-C cable. If you use a battery case or always dock at your desk, you can even drop to 5,000–7,500 mAh for emergencies.
Content Days And Events
When you shoot video or tether data, your phone drains fast. Step up to 15,000–20,000 mAh so you can record, edit, and navigate without rationing screen time. Add a 30 W USB-C PD port to keep speeds up while you use the device.
Tablet Work Or Console Play
For iPad-class tablets and handheld consoles, start at 20,000 mAh. If you travel or share with a partner, 25,000–30,000 mAh buys breathing room and fewer nightly recharges.
Light Laptop Top-Ups
Some thin-and-light notebooks accept a boost over USB-C. Here, the pack’s wattage matters more than raw mAh. Aim for 20,000–30,000 mAh with a 45–65 W PD port and a certified high-current cable.
How To Convert mAh To Wh Yourself
Use the simple formula: Wh = (mAh × V) ÷ 1000. If the label shows 3.7 V, multiply the mAh by 3.7 and divide by 1000. That’s your Wh. This number matters for airline limits and for comparing across products that list energy in Wh instead of mAh.
Buying Checklist
- Capacity target: 10,000 mAh for daily carry; 15,000–20,000 mAh for heavy phone use; 20,000–30,000 mAh for tablets or shared charging.
- Speed: USB-C PD with at least 20–30 W for phones; 45–65 W if you plan to juice a laptop.
- Cable: Use a cable that matches the wattage; EPR-rated for high-power devices.
- Ports: One USB-C in/out plus a second USB-C or USB-A.
- Air travel: Keep packs under 100 Wh for smooth screening; carry in cabin bags.
- Safety: Protections listed, clear labeling, and a real warranty.
Why This Guidance Tracks With Real-World Data
Phone batteries cluster near 3,500–5,000 mAh, while large models push past that. Independent testing often finds the 10,000 mAh class delivering a touch under two phone refills, with 20,000 mAh roughly doubling that. USB-IF documentation confirms modern USB-C PD can supply far higher wattage than legacy chargers, so a well-matched pack charges faster and runs cooler during heavy use.
Final Take
If you want a simple rule: carry 10,000 mAh for daily phone use, move to 15,000–20,000 mAh when you push your phone hard or manage two devices, and pick 20,000–30,000 mAh if a tablet or console is part of your day. Match the wattage to your device, bring a proper cable, and check Wh when you fly. That’s the stress-free way to choose capacity and get on with your day.
Facts in this guide reference open standards and airline rules. Where linked, those pages explain the formulas and limits used here.