# How long can Omnicharge charge your laptop?Updated 10 months ago

This question involves some complexity due to the variable power consumption of your laptop, depending on whether you're gaming or simply browsing the internet. This variability impacts the time and percentage of charge that Omnicharge can provide to your laptop.

We adopt a more objective approach to simplify matters by comparing Omnicharge's battery capacity to the laptop's internal battery. This also takes into account the efficiency losses in both Omnicharge's AC conversion circuits and the laptop's power adapter. The equation for calculating the charge percentage is as follows:

**Omnicharge's battery capacity / laptop's internal battery capacity * Omnicharge's conversion circuits efficiency * laptop's power supply efficiency**

For instance, let's consider the Omni 40+ and the 15'' MacBook Pro (2019 model). The Omni 40+ has a battery capacity of **142Wh**, and the 15'' MacBook Pro has an internal battery capacity of **83.6Wh**. Both the Omnicharge's conversion efficiency and the 15'' MacBook Pro's power supply efficiency is approximately** 90%**. Plugging in these values into the equation yields:

**142Wh / 83.6Wh * 90% * 90% = 1.38**

This implies that the Omnicharge can charge the 15'' MacBook Pro around **1.4 times**, assuming the laptop is either turned off or in sleep mode. However, using the laptop while charging will influence this calculation.

----------------------------**Moving on to the USB-C output:**

One of the benefits of the USB-C output is that you don't need to contend with the efficiency loss of the laptop's power supply. Thus, the equation simplifies to:

**Omnicharge's battery capacity / laptop's internal battery capacity * Omnicharge's conversion circuits efficiency **

Again take the Omni 40+ and 15'' MacBook Pro for example:

**142Wh / 83.6Wh * 90% = 1.53**

This signifies that the Omnicharge can charge the 15'' MacBook Pro around **1.5 times**. Notably, this is **10****%** more compared to charging from the AC outlet!