Today, I looked at my AncestryDNA results with my two closest matches – my sister’s two daughters. I hadn’t compared the amount of shared DNA between us before today when I was looking to see if there were new close matches on AncestryDNA.
Shared DNA between me, niece 1 (the older sister), and niece 2 (the younger sister).
Niece 1: 1,742 centimorgans shared across 62 DNA segments
Niece 2: 1,603 centimorgans shared across 66 DNA segments
What are centiMorgans – https://isogg.org/wiki/CentiMorgan
Neither niece has uploaded to GEDmatch: https://www.gedmatch.com/login1.php. Nor have they uploaded to other sites. There are a number of free limited transfer websites out there – MyHeritageDNA, FamilyTree DNA (FTDNA), GEDmatch, and DNA.Land. Promethease (health, not genealogy, related) I believe is free for a while longer.