Should I replace my battery?

It’s just below the 80% mark. See .this article.

scroll through to see battery % and what different one means. You probably should get new battery for the phone. EDIT: get the battery replace before December 31 for $29 because after will cost $49.

https://support.apple.com/en-us/HT208387

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Hi ve7878,

Welcome to Apple Support Communities. I understand you have some questions about the health of your battery on your iPhone 6s. I know it's important to be sure you're getting the most from the battery; I'd like to help. I'd recommend taking a look at the information titled"Battery Health" to learn more about your battery's capacity: iPhone Battery and Performance

You can also use the resources below to see how your battery is being used and steps you can take to get the best performance:

About the battery usage on your iPhone, iPad, and iPod touch

Maximizing Battery Life and Lifespan

Should you decide you'd like to look into a replacement battery, take a look at the information in this link: iPhone service pricing

Best Regards.