Wh to mAh Calculator

Watt hours measure energy and milliamp hours measure charge, so there is no conversion between the two until a voltage is fixed. Enter the energy in watt hours, kilowatt hours or joules along with the pack voltage, and this returns the capacity in mAh and in Ah. A second action restates a rating taken at cell voltage as the capacity at the voltage the pack actually delivers, with an efficiency allowance for the converter. That is why a 20,000 mAh power bank is worth nearer 14,800 mAh once it is measured at 5 V.

Calculator Type
Energy Unit
The nominal voltage of the cells, printed on the pack or in its datasheet. One lithium ion cell is 3.6 or 3.7 V, a LiFePO4 cell 3.2 V, a NiMH cell 1.2 V, an alkaline cell 1.5 V, a lead acid block 12 V. A pack of cells in series multiplies it.
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Capacity Unit
The nominal voltage of the cells, printed on the pack or in its datasheet. One lithium ion cell is 3.6 or 3.7 V, a LiFePO4 cell 3.2 V, a NiMH cell 1.2 V, an alkaline cell 1.5 V, a lead acid block 12 V. A pack of cells in series multiplies it.
The voltage the pack actually delivers. A USB-A port is 5 V; USB Power Delivery negotiates 9, 12, 15 or 20 V.
Leave at 100 for the pure arithmetic. A real boost converter in a power bank runs about 80 to 90 per cent, and the loss shows up as heat.
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