Ah to mAh Calculator
This calculator converts battery capacity from amp-hours (Ah) to milliamp-hours (mAh). It helps translate large-scale energy units into those used in phones, wearables, and small electronics.
What Is the Difference Between Ah and mAh?
Both ampere-hours (Ah) and milliampere-hours (mAh) are units of electric charge used to describe battery capacity — in other words, how much current a battery can deliver over time. The only difference between the two lies in the scale:
- 1 Ah = 1 amp for 1 hour
- 1 mAh = 1 milliamp for 1 hour = 0.001 Ah
This means:
1 Ah = 1000 mAh
While Ah is typically used for large batteries (UPS, car, solar, industrial), mAh is used for smaller ones (phones, power banks, watches). Converting between the two is essential when comparing, estimating, or translating specifications across battery sizes.
Conversion Formula: Ah to mAh
The formula is extremely simple:
mAh = Ah × 1000
Example 1: A battery rated at 2.5 Ah
2.5 Ah × 1000 = 2500 mAh
Example 2: A battery bank of 120 Ah
120 Ah × 1000 = 120,000 mAh
This conversion is especially useful if you're trying to compare a small consumer-grade battery with a larger, system-level energy source.
When Should You Use This Conversion?
- Product comparison: Comparing power banks labeled in mAh with battery packs labeled in Ah
- Micro vs macro planning: Aligning small device loads (mAh) with large battery banks (Ah)
- Purchasing decisions: Interpreting technical specifications across brands or product types
- Marketing clarity: Consumer electronics often use mAh for readability, even if internal batteries are rated in Ah
Real-World Examples
- Smartphone battery: 3.7V, 3000 mAh = 3 Ah battery
- USB power bank: Often 10,000 mAh, which is 10 Ah at 3.7V
- Car battery: Usually around 50–70 Ah = 50,000–70,000 mAh
- Solar battery bank: A 200 Ah 12V battery system = 200,000 mAh at 12V
Common Devices and Their Battery Ratings
| Device | Typical Capacity | Voltage |
|---|---|---|
| Smartphone | 3000 – 5000 mAh | 3.6–3.85V |
| Wireless earbuds | 30 – 80 mAh | 3.7V |
| Laptop | 4000 – 8000 mAh | 11.1 – 14.8V |
| Portable power bank | 5000 – 20000 mAh | 3.7V (internal) |
| 12V AGM battery | 50 – 120 Ah | 12V |
Why Do Some Devices Use mAh and Others Use Ah?
It’s largely a matter of convention and readability. Small devices use mAh because it gives numbers that feel intuitive to the average user (e.g., 5000mAh instead of 5Ah). For larger energy systems, using Ah is more practical to avoid large, unwieldy numbers. Both units describe the same physical quantity — electric charge — just in different scales.
Estimating Runtime Using mAh or Ah
You can use either unit to estimate how long a battery will last based on a device's current draw:
Runtime (hours) = mAh ÷ current draw (mA)
Or if you're using Ah:
Runtime (hours) = Ah ÷ current draw (A)
Example: A 10,000 mAh power bank powers a 1000 mA device:
10,000 ÷ 1000 = 10 hours of runtime
Frequently Asked Questions (FAQ)
Is mAh the same as battery life?
No — mAh tells you how much charge a battery can hold. Battery life also depends on how fast that charge is used (the current draw), device efficiency, voltage, and power conversion losses.
Can I convert mAh to Ah directly?
Yes — it's the reverse of this calculator:
Ah = mAh ÷ 1000
Why do some manufacturers list only Ah?
Industrial and automotive batteries are typically large enough that Ah is more readable than mAh. For example, a 100Ah battery would otherwise be listed as 100,000 mAh — unnecessarily large for a label.
Can I use Ah or mAh for all battery chemistries?
Yes. This conversion applies to lithium-ion, lead-acid, NiMH, NiCd, etc. But voltage still matters when calculating energy (Wh).
What if a battery has no mAh or Ah listed?
Check for watt-hours (Wh) and voltage (V). You can calculate Ah using:
Ah = Wh ÷ V, then multiply by 1000 to get mAh.
Conclusion
Converting amp-hours (Ah) to milliamp-hours (mAh) is simple but extremely helpful when comparing batteries, estimating runtimes, or translating between consumer and industrial products. As battery technology becomes increasingly integrated into everyday life — from phones and laptops to solar systems and electric vehicles — having an intuitive grasp of charge units like mAh and Ah is essential for making smart energy decisions.