21 mAh Is How Many Wh?

Quick Answer: 21 mAh = 0.0777 Wh (at 3.7V)

mAh → Wh Wh → mAh
Milliamp-hours
=
Watt-hours
Auto-fills voltage
Nominal battery voltage
Conversion Result
21 mAh = 0.0777 Wh (at 3.7V)

At 3.7V nominal voltage

21 mAh = 0.0777 Wh (at 3.7V)

Step-by-step:

  1. Formula: Wh = mAh × V / 1,000
  2. 21 × 3.7 / 1,000 = 0.0777 Wh

Similar mAh to Wh Conversions

Values close to 21 mAh (at 3.7V Li-ion):

mAh Wh (at 3.7V)
1 mAh 0.0037 Wh
11 mAh 0.0407 Wh
21 mAh 0.0777 Wh
31 mAh 0.1147 Wh
41 mAh 0.1517 Wh
51 mAh 0.1887 Wh
61 mAh 0.2257 Wh
71 mAh 0.2627 Wh

Popular mAh to Wh Conversions

2,500 mAh9.25 Wh 3,000 mAh11.1 Wh 3,500 mAh12.95 Wh 4,000 mAh14.8 Wh 5,000 mAh18.5 Wh 6,000 mAh22.2 Wh 10,000 mAh37 Wh 15,000 mAh55.5 Wh 20,000 mAh74 Wh 26,800 mAh99.16 Wh 50,000 mAh185 Wh 500 mAh1.85 Wh

See Also

Frequently Asked Questions

How many Wh is 21 mAh?

21 mAh equals 0.0777 Wh at 3.7V (Li-ion nominal voltage). The exact Wh depends on the battery voltage: Wh = mAh × V / 1,000.

How do I convert 21 mAh to Wh?

Multiply 21 by the battery voltage, then divide by 1,000. At 3.7V: 21 × 3.7 / 1,000 = 0.0777 Wh.

Is 21 mAh allowed on a plane?

At 3.7V, 21 mAh = 0.0777 Wh. Airlines allow lithium batteries up to 100 Wh in carry-on luggage. Batteries between 100–160 Wh require airline approval. Batteries over 160 Wh are prohibited on passenger aircraft.

More mAh to Wh conversions

Formula: Wh = mAh × V / 1,000. Results assume nominal battery voltage.

Conversion factors verified against NIST, BIPM Based on SI definitions (BIPM). Last reviewed: March 2026
Adilson Fernandes By Adilson Fernandes
Tiago Fernandes Reviewed by Tiago Fernandes