How much charger
do you actually need?
Add your device targets. See the combined output and port requirements before comparing adapters.
Check the whole charger and each port.
Example: two devices charging at the same time.
Check these targets against the allocation table
- Device 165 W
- Device 220 W
- Device 3Unused
A headline rating of 85 W or more does not prove that two ports can supply 65 W and 20 W together.
This is a budget, not a compatibility test. Output wattages, USB PD/PPS profiles, cable ratings and the charger’s power-sharing rules must all fit your devices. A larger printed wattage alone does not establish support or guarantee charging speed.
Three checks before you buy
The calculation is deliberately simple. Choosing a working charging setup also requires the details that a large number on a box can hide.
Read the charger buying checklist →Start with the device, not the adapter
Use the manufacturer’s recommended charging setup for your exact model. A device’s charging target differs from its battery capacity, and a supplied adapter’s label does not mean the device draws that power continuously.
Read the multiport allocation table
For simultaneous charging, check the exact combination of ports. Enough total output is necessary to meet all the targets you entered, but a charger can still divide that total in a way that does not suit your kit.
Match the profiles and cables
Check USB Power Delivery, any model-specific PPS requirements, the supported voltage/current profiles, and cable ratings. Wattage arithmetic cannot verify those capabilities or predict a charge time.
65 W + 20 W does not automatically mean “buy a 100 W charger.”
A hypothetical laptop target of 65 W and phone target of 20 W add up to 85 W when charged together. The adapter must also provide those individual targets on the ports you will use. A 100 W headline alone does not tell you its two-port allocation.
If you are happy to charge them one at a time, a suitable single port with a 65 W output target may cover both turns, provided the required profiles and cables match each device. You trade simultaneous charging for a lower combined power requirement.
The planner does not add an arbitrary percentage of extra wattage. Any additional capacity is your choice for a documented need, such as another device, rather than a claim that every kit requires it.
Keep building your charging kit
Sources and limits
This editorial tool performs arithmetic on the values you enter. It does not inspect your devices, measure current, certify a charger, guarantee compatibility, or recommend a purchase based on a test. Illustrative presets are not model specifications. Source guidance checked October 24, 2026.
- USB-IF: USB Charger and USB Power Delivery — the protocol’s power capabilities and device negotiation.
- Apple: Use a power adapter with your Mac — identifying the recommended adapter and checking delivered wattage.
- Google: 45W USB-C Power Charger specifications — an example of separate PD/PPS voltage and current profiles.
Devices reduce or vary their draw with battery state, temperature and use. A manufacturer’s specified profile and allocation table take precedence over this planning arithmetic. See how we research and evaluate products.