Wh to mAh Conversion: Formula, Chart, and Real-World Battery Examples
This guide explains how to convert watt-hours to milliamp-hours using voltage, why Wh is more reliable than mAh for comparing batteries, and how to apply the formula to power banks, airline battery limits, and UDPOWER portable power stations. It includes clear charts, real-world examples, runtime planning tips, and product recommendations for choosing the right backup power solution.
Last updated: July 7, 2026
Quick Answer: How Do You Convert Wh to mAh?
To convert watt-hours to milliamp-hours, multiply Wh by 1,000, then divide by voltage.
mAh = Wh × 1000 ÷ VExample: a 100Wh battery equals about 27,027mAh at 3.7V, 20,000mAh at 5V, or 8,333mAh at 12V. That is why voltage matters. A mAh number by itself does not tell you how much real energy a battery stores.
For comparing portable power stations, power banks, laptop batteries, and solar generators, Wh is the more reliable number. Use mAh only when the voltage is also listed.
Wh to mAh Formula
The standard Wh to mAh formula is:
mAh = Wh × 1000 ÷ VIn this formula, Wh means watt-hours, mAh means milliamp-hours, and V means voltage. The number 1,000 converts amp-hours into milliamp-hours.
Example: Convert 50Wh to mAh at 3.7V
50 × 1000 ÷ 3.7 = 13,514mAh
The same 50Wh battery at 5V would be 10,000mAh. At 12V, it would be 4,167mAh. The stored energy is the same, but the mAh number changes because the voltage changes.
Reverse Formula: mAh to Wh
To convert mAh back to Wh, use:
Wh = mAh × V ÷ 1000Example: a 20,000mAh power bank at 3.7V is 74Wh. A 20,000mAh battery at 12V is 240Wh. Same mAh, very different energy.
Why Voltage Changes the mAh Number
mAh measures electric charge at a specific voltage. Wh measures stored energy. That is the reason Wh is better for fair comparisons.
A small USB power bank may advertise 20,000mAh because the internal lithium-ion cells are commonly rated around 3.6V to 3.7V. A portable power station, however, may use a higher-voltage battery pack and list capacity in Wh because Wh tells you how much energy is available to run real devices.
The simple rule
When shopping for backup power, use Wh for capacity and W for output. Capacity tells you how long a device may run. Output tells you whether the power station can run the device at all.
For a step-by-step device compatibility guide, read How Do You Know if a Portable Power Station Can Power Your Device?.
Wh to mAh Conversion Chart
Use this table when you know the battery capacity in Wh and want to see the mAh equivalent at common voltages.
| Watt-hours | mAh at 3.7V | mAh at 5V | mAh at 12V | Best real-world use |
|---|---|---|---|---|
| 1Wh | 270mAh | 200mAh | 83mAh | Small cells, sensors, tiny electronics |
| 5Wh | 1,351mAh | 1,000mAh | 417mAh | Small rechargeable accessories |
| 10Wh | 2,703mAh | 2,000mAh | 833mAh | Phone battery comparison |
| 20Wh | 5,405mAh | 4,000mAh | 1,667mAh | Compact power banks |
| 37Wh | 10,000mAh | 7,400mAh | 3,083mAh | Typical 10,000mAh power bank at cell voltage |
| 50Wh | 13,514mAh | 10,000mAh | 4,167mAh | Small laptop battery range |
| 74Wh | 20,000mAh | 14,800mAh | 6,167mAh | Typical 20,000mAh power bank at cell voltage |
| 100Wh | 27,027mAh | 20,000mAh | 8,333mAh | Common airline battery limit |
| 160Wh | 43,243mAh | 32,000mAh | 13,333mAh | Upper airline approval range for many spare lithium batteries |
| 256Wh | 69,189mAh | 51,200mAh | 21,333mAh | Compact portable power station class |
| 596Wh | 161,081mAh | 119,200mAh | 49,667mAh | Road trip, router, CPAP, light camping backup |
| 1,190Wh | 321,622mAh | 238,000mAh | 99,167mAh | Refrigerator, CPAP, home essentials |
| 2,083Wh | 562,973mAh | 416,600mAh | 173,583mAh | High-capacity home backup and RV use |
Formula reference: RapidTables Wh to mAh calculator and Goal Zero watt-hour calculator.
mAh to Wh Conversion Chart
Use this table when a battery only lists mAh. If the voltage is not printed on the label, do not assume the Wh value for safety, travel, or device planning.
| mAh rating | Wh at 3.7V | Wh at 5V | What it usually means |
|---|---|---|---|
| 5,000mAh | 18.5Wh | 25Wh | Small phone power bank |
| 10,000mAh | 37Wh | 50Wh | Everyday portable charger |
| 20,000mAh | 74Wh | 100Wh | Large phone or tablet power bank |
| 26,800mAh | 99.16Wh | 134Wh | Near the 100Wh travel threshold if rated at 3.7V |
| 30,000mAh | 111Wh | 150Wh | May require airline approval or be restricted |
| 50,000mAh | 185Wh | 250Wh | Too large for many passenger-flight power bank rules |
| 100,000mAh | 370Wh | 500Wh | Power station territory; use Wh instead of mAh |
For the reverse calculation, see UDPOWER’s mAh to Wh Conversion Guide.
Which Voltage Should You Use?
This is the part that causes the most confusion. The correct voltage depends on what you are trying to compare.
| Situation | Voltage to use | Why it matters | Better number to compare |
|---|---|---|---|
| Power bank advertised in mAh | Usually 3.6V–3.7V cell voltage, if printed or stated by the brand | Power bank marketing often uses internal cell voltage, not USB output voltage | Wh |
| USB output calculation | 5V, 9V, 12V, 20V, or the actual USB-C PD output profile | Output voltage changes during fast charging, so mAh can be misleading | Wh and output watts |
| Portable power station comparison | Use the official Wh rating first | Portable stations may use multi-cell battery packs and inverters | Wh, AC output W, surge W |
| 12V DC device planning | 12V or the device’s actual DC voltage | Useful for fans, routers, DC fridges, and vehicle-style sockets | Wh and device watts |
| Air travel battery check | Use the Wh printed on the battery label whenever available | Airlines and regulators commonly use Wh limits | Wh |
Do not compare two batteries by mAh unless the voltage is the same.
A 20,000mAh battery at 3.7V stores 74Wh. A 20,000mAh battery at 12V stores 240Wh. The mAh number looks identical, but the real energy is not.
UDPOWER Product Examples: Convert Real Wh Ratings to mAh
UDPOWER portable power stations list capacity in Wh because Wh is the most useful number for real devices. The mAh values below are equivalents at common comparison voltages. They are not a replacement for the official Wh rating.
| UDPOWER model | Official capacity | AC output | mAh equivalent at 3.7V | mAh equivalent at 5V | Source |
|---|---|---|---|---|---|
| UDPOWER C400 | 256Wh | 400W | 69,189mAh | 51,200mAh | C400 product page |
| UDPOWER C600 | 596Wh | 600W | 161,081mAh | 119,200mAh | C600 product page |
| UDPOWER S1200 | 1,190Wh | 1,200W | 321,622mAh | 238,000mAh | S1200 product page |
| UDPOWER S2400 | 2,083Wh | 2,400W | 562,973mAh | 416,600mAh | S2400 product page |
These examples show why power stations should not be judged like phone power banks. A 1,190Wh station may convert to a very large mAh number at 3.7V, but that number does not tell you whether it can run a refrigerator, coffee maker, CPAP machine, or power tool. For that, check both capacity in Wh and output in W.
How Wh Helps Estimate Runtime
Once you know Wh, runtime is much easier to estimate. Use this simple planning formula:
Estimated runtime = battery Wh × 0.90 ÷ device wattsThe 0.90 factor allows for real-world conversion loss. Actual runtime can vary with inverter load, device cycling, temperature, battery age, and whether you are using AC or DC output.
| Device | Estimated watts | C400 256Wh | C600 596Wh | S1200 1,190Wh | S2400 2,083Wh |
|---|---|---|---|---|---|
| Phone charging | 10W | 23.0 hrs | 53.6 hrs | 107.1 hrs | 187.5 hrs |
| WiFi router | 12W | 19.2 hrs | 44.7 hrs | 89.2 hrs | 156.2 hrs |
| Laptop | 60W | 3.8 hrs | 8.9 hrs | 17.9 hrs | 31.2 hrs |
| CPAP without humidifier | 40W | 5.8 hrs | 13.4 hrs | 26.8 hrs | 46.9 hrs |
| Mini fridge, continuous estimate | 70W | 3.3 hrs | 7.7 hrs | 15.3 hrs | 26.8 hrs |
| Full-size refrigerator, continuous compressor estimate | 150W | 1.5 hrs | 3.6 hrs | 7.1 hrs | 12.5 hrs |
Refrigerator runtime can be longer than a continuous-watt estimate because many refrigerators cycle on and off. For a deeper breakdown, see Can a Portable Power Station Run Your Refrigerator?.
Recommended UDPOWER Models by Battery Size
The best model depends on what you need to power. Start with Wh for runtime, then check AC output watts and surge needs.
UDPOWER C400 — Compact Camping and Device Backup
The C400 is a practical choice for phones, laptops, small fans, camping lights, drone batteries, and short backup needs. Its 256Wh capacity is much larger than a typical phone power bank, and the 400W AC output gives it more flexibility for small AC devices.
- Capacity: 256Wh
- AC output: 400W
- mAh equivalent at 3.7V: about 69,189mAh
- Best for: short camping trips, laptop backup, lights, fans, portable electronics
UDPOWER C600 — More Runtime for Road Trips and CPAP Backup
The C600 steps up to 596Wh, making it better for overnight device charging, routers, CPAP use without heating, longer laptop backup, and light off-grid setups.
- Capacity: 596Wh
- AC output: 600W
- mAh equivalent at 3.7V: about 161,081mAh
- Best for: road trips, router backup, CPAP, longer camping power
UDPOWER S1200 — Home Essentials and Refrigerator Backup
The S1200 is the better fit when you need more than device charging. With 1,190Wh capacity and 1,200W AC output, it is built for higher-demand backup situations such as refrigerators, CPAP machines, routers, TVs, and emergency essentials.
- Capacity: 1,190Wh
- AC output: 1,200W
- mAh equivalent at 3.7V: about 321,622mAh
- Best for: home backup, refrigerator support, CPAP, emergency power, camping comfort
UDPOWER S2400 — Larger Backup Loads and RV Power
The S2400 gives you 2,083Wh capacity and 2,400W AC output, making it a stronger option for RV trips, power tools, microwave-class loads, and longer emergency backup planning.
- Capacity: 2,083Wh
- AC output: 2,400W
- mAh equivalent at 3.7V: about 562,973mAh
- Best for: RV use, higher-watt appliances, longer outages, heavier backup needs
For a side-by-side model overview, visit the UDPOWER Power Station Comparison page or browse all portable power stations.
Airline Battery Limits: Why Wh Matters More Than mAh
Airlines and aviation safety rules commonly use Wh, not mAh, because Wh shows stored energy more clearly. If your power bank only lists mAh, convert it to Wh before traveling.
| Battery label | Assumed voltage | Calculated Wh | Travel meaning |
|---|---|---|---|
| 10,000mAh | 3.7V | 37Wh | Usually below the common 100Wh threshold |
| 20,000mAh | 3.7V | 74Wh | Usually below the common 100Wh threshold |
| 26,800mAh | 3.7V | 99.16Wh | Close to the 100Wh line; label clarity matters |
| 30,000mAh | 3.7V | 111Wh | May require airline approval and may be restricted |
| Portable power station above 160Wh | Varies | Usually over airline passenger limits | Do not assume it can fly as a carry-on power bank |
Travel reference: FAA PackSafe lithium battery guidance. Always check your airline’s current rule before flying.
Common Wh to mAh Mistakes to Avoid
1. Comparing mAh numbers without voltage
A 20,000mAh power bank and a 20,000mAh 12V battery do not store the same energy. Convert both to Wh first.
2. Confusing Wh with W
Wh is capacity. W is output or power draw. A 1,190Wh power station with 1,200W output has enough capacity for runtime planning and enough output for many higher-watt devices, but you still need to check each device’s running watts and startup surge.
3. Using USB output voltage for internal battery capacity
Many power banks advertise capacity using internal cell voltage, often around 3.7V. USB output may be 5V, 9V, 12V, or 20V. That is why delivered charge to your phone or laptop can look lower than the printed mAh number.
4. Ignoring efficiency loss
Inverters and voltage converters use some energy. For quick planning, use Wh × 0.90 ÷ device watts. For critical devices, leave extra margin.
5. Treating power station mAh as a buying shortcut
For power stations, mAh can make capacity look huge but does not help much by itself. Buy based on Wh, AC output, surge capacity, ports, recharge options, and the devices you need to run.
Wh to mAh Conversion FAQ
How do you convert Wh to mAh?
Use mAh = Wh × 1000 ÷ V. You need the battery voltage to get an accurate answer.
How many mAh is 1Wh?
At 3.7V, 1Wh is about 270mAh. At 5V, 1Wh is 200mAh. At 12V, 1Wh is about 83mAh.
How many mAh is 100Wh?
100Wh is about 27,027mAh at 3.7V, 20,000mAh at 5V, or 8,333mAh at 12V.
How many Wh is 20,000mAh?
At 3.7V, 20,000mAh equals 74Wh. At 5V, it equals 100Wh. At 12V, it equals 240Wh.
Is Wh better than mAh?
Yes, Wh is better for comparing batteries with different voltages because it measures stored energy. mAh is only useful when the voltage is also known.
Why do power banks use mAh but power stations use Wh?
Power banks are often marketed around small lithium cell capacity, so mAh is common. Portable power stations run larger devices and use inverters, so Wh gives a clearer picture of usable energy and runtime.
Can I compare two batteries by mAh?
Only if both batteries use the same voltage. If the voltages are different, convert both to Wh first.
What voltage should I use for a power bank?
Use the voltage printed on the power bank label. Many lithium-ion power banks use about 3.7V for internal cell capacity, but you should confirm the label or manual.
What voltage should I use for a portable power station?
For buying and runtime planning, use the official Wh rating first. A mAh conversion can be shown for comparison, but Wh is the more useful capacity number for portable power stations.
Does mAh tell me how long a battery will last?
Not by itself. For runtime, use Wh and device watts: runtime ≈ Wh × efficiency ÷ device watts.
Are airline battery limits based on Wh or mAh?
Airline battery rules commonly use Wh. If a power bank only lists mAh, convert it to Wh using the voltage shown on the label and check your airline’s current policy.
Can I take a portable power station on a plane?
Most portable power stations exceed common passenger lithium battery limits. Always check the Wh rating and your airline’s policy before travel.
Need More Than a Power Bank?
If your goal is to run a refrigerator, CPAP machine, router, laptop, fan, TV, or camping setup, do not shop by mAh alone. Compare capacity in Wh, output in W, and the actual devices you plan to power.
Start with the UDPOWER Portable Power Station Collection, compare models on the Product Comparison page, or use the Battery Unit Conversion Tools to check your numbers.
View Portable Power Stations Compare UDPOWER ModelsRelated Articles
