How to Calculate Battery Watt-Hours for Shipping

Airlines classify lithium-ion batteries by watt-hour rating. Knowing the Wh of your battery tells you which packing instruction and which limits apply.

On this pageThe watt-hour formula Where to find the numbers Air-shipping thresholds (lithium-ion)Lithium metal: use grams, not Wh Why it matters for your shipment

The watt-hour formula

Wh = Voltage (V) × Ampere-hours (Ah)

If your battery spec shows milliampere-hours (mAh) instead of Ah, divide by 1000 first. Example: a 3.7 V, 5000 mAh cell = 3.7 × 5.0 = 18.5 Wh.

Where to find the numbers

Printed on the battery label (most compliant cells show V and Ah/Wh)
In the product datasheet or UN38.3 test summary
On the manufacturer's specification page

If the label already shows "Wh", you can use that directly and skip the math.

Air-shipping thresholds (lithium-ion)

Rating	Air rule (passenger & cargo)
≤ 100 Wh	Generally permitted; small quantities may use Section II simplified rules
100-160 Wh	Allowed with operator approval; stricter packing (PI965 IB / PI966-967)
> 160 Wh	Cargo aircraft only; not in passenger baggage

Lithium metal: use grams, not Wh

Non-rechargeable lithium metal batteries are limited by lithium content in grams, not watt-hours. The common limit is 1 g per cell and 2 g per battery for many exceptions; confirm against the current IATA limit for your configuration.

Why it matters for your shipment

Determines the packing instruction (PI965-970) and whether a dangerous goods declaration is needed
Affects whether the battery can travel in passenger aircraft or cargo only
Influences packaging, labeling (Class 9 label, lithium mark), and state-of-charge limits

Keep the UN38.3 test summary available - carriers and airlines can request it. Batteries that cannot show compliance may be refused.

Frequently Asked Questions

My battery shows mAh, how do I get Wh?

Convert mAh to Ah by dividing by 1000, then multiply by voltage. 5000 mAh at 3.7 V = 18.5 Wh.

What if there is no Wh on the label?

Calculate it from V and Ah, or ask the manufacturer for the UN38.3 summary which states the rated Wh.

Do these limits apply to sea freight?

Sea (IMDG) uses the same Wh concept for classification but allows larger quantities and different stowage; the 100/160 Wh passenger-baggage thresholds are an air rule.