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mAh to Ah

1 Milliamp-hour (mAh) = 0.001 Amp-hour (Ah)

Result
0.001 Ah
1 mAh = 0.001 Ah

How Many Amp-hours in a Milliamp-hour?

To convert milliamp-hours to amp-hours, divide the number of milliamp-hours by 1,000. The formula is Ah = mAh ÷ 1,000. For example, 5,000 mAh equals 5 Ah. This conversion bridges the two most common units for expressing battery capacity — milliamp-hours for small consumer electronics and amp-hours for larger batteries. Smartphone batteries, power banks, wireless earbuds, and portable chargers list capacity in mAh, while car batteries, deep-cycle marine batteries, solar energy storage systems, and electric vehicle batteries use Ah. Understanding this conversion helps you compare battery capacities across different product categories, calculate charging times, and evaluate whether a portable battery can adequately charge your devices.

How to Convert Milliamp-hour to Amp-hour

  1. Start with the battery capacity in milliamp-hours (mAh).
  2. Divide by 1,000 to get amp-hours (Ah).
  3. The result is the capacity expressed in amp-hours.
  4. Simply move the decimal point three places to the left.
  5. For example: 10,000 mAh → 10.000 Ah → 10 Ah.

Real-World Examples

Smartphone battery — An iPhone with a 3,279 mAh battery
3,279 ÷ 1,000 = 3.279 Ah. This is a relatively small capacity compared to laptop or car batteries.
Power bank — A portable charger rated at 20,000 mAh
20,000 ÷ 1,000 = 20 Ah. At 5V, this stores 100 Wh of energy — close to the 100 Wh limit for airline carry-on batteries.
Laptop battery — A 6-cell laptop battery at 4,400 mAh
4,400 ÷ 1,000 = 4.4 Ah. At the laptop's typical 11.1V, this represents about 48.8 Wh of energy storage.
Drone battery — A LiPo battery rated at 5,200 mAh
5,200 ÷ 1,000 = 5.2 Ah. At 14.8V (4S LiPo), this is 77 Wh — enough for about 20-30 minutes of flight.
Comparing phone to car battery — 4,000 mAh phone vs. 60 Ah car battery
4,000 ÷ 1,000 = 4 Ah. The car battery is 60 Ah ÷ 4 Ah = 15 times the capacity of the phone battery (and at much higher voltage, making the energy difference even larger).

Quick Reference

Milliamp-hour (mAh) Amp-hour (Ah)
1 0.001
2 0.002
5 0.005
10 0.01
25 0.025
50 0.05
100 0.1
500 0.5
1,000 1

History of Milliamp-hour and Amp-hour

Battery capacity measurement in milliamp-hours and amp-hours evolved alongside battery technology. Early batteries — like the Voltaic pile (1800) and the Daniell cell (1836) — had no standardized capacity measurement. As rechargeable lead-acid batteries became common in the late 1800s for telegraphy and early automobiles, the amp-hour became the standard measure of how much charge a battery could store and deliver. The milliamp-hour gained prominence with the portable electronics revolution. When Sony introduced the first commercial lithium-ion battery in 1991, it was rated at 1,000 mAh — a capacity that seemed enormous for the era. Today's smartphone batteries range from 3,000 to 6,000 mAh, while high-capacity power banks reach 30,000 mAh or more. It is important to understand that mAh and Ah measure electric charge (current × time), not energy. A 5,000 mAh battery at 3.7V stores 18.5 Wh of energy, while a 5,000 mAh battery at 7.4V stores 37 Wh. This is why comparing batteries of different voltages by mAh alone can be misleading — watt-hours (Wh) is the more complete measure of total energy storage.

Common Mistakes to Avoid

  • Multiplying instead of dividing. To go from mAh to Ah, divide by 1,000 — the number gets smaller. A 5,000 mAh battery is 5 Ah, not 5,000,000 Ah.
  • Comparing mAh across different voltages as if they represent the same energy. A 10,000 mAh power bank at 3.7V stores 37 Wh, but it delivers at 5V via USB. Due to voltage conversion losses, it can actually charge about 6,660 mAh at 5V — not the full 10,000 mAh that the label suggests.
  • Assuming a battery rated at X mAh can supply X mA for exactly one hour. Battery capacity varies with discharge rate — high-current draws reduce effective capacity. A battery rated at 2,000 mAh at the 1C rate (2,000 mA) might deliver 2,200 mAh if discharged slowly (0.5C) or only 1,800 mAh at a high discharge rate (2C).

Frequently Asked Questions

How many amp-hours is 1 milliamp-hour?
One milliamp-hour equals 0.001 amp-hours (one-thousandth of an amp-hour). The "milli" prefix means one-thousandth.
Why do phone batteries use mAh while car batteries use Ah?
It is purely about scale and readability. Phone batteries are typically 3,000-6,000 mAh (3-6 Ah), so mAh avoids decimals. Car batteries are 40-100 Ah, so amp-hours give clean whole numbers. The underlying unit is the same — just shifted by a factor of 1,000.
How do I calculate how many times a power bank can charge my phone?
Divide the power bank's mAh by the phone's battery mAh, then multiply by about 0.65-0.7 to account for voltage conversion and transfer losses. Example: 20,000 mAh power bank with a 4,000 mAh phone = (20,000 ÷ 4,000) × 0.67 ≈ 3.35 full charges.
What is the airline limit for battery capacity?
Most airlines limit carry-on lithium batteries to 100 Wh (watt-hours). To check if your power bank complies, multiply its mAh by its voltage and divide by 1,000: a 27,000 mAh power bank at 3.7V = 27,000 × 3.7 ÷ 1,000 = 99.9 Wh — just barely under the limit.
Quick Tip

When shopping for power banks, do not trust the mAh number at face value. The rated mAh is measured at the internal battery voltage (usually 3.7V), but USB output is at 5V. The effective capacity at 5V is roughly 65-70% of the rated mAh after accounting for voltage conversion and heat losses. A "20,000 mAh" power bank effectively delivers about 13,000-14,000 mAh at 5V. For a more accurate comparison between power banks, look for the watt-hour (Wh) rating if available.