Great comparison, especially the discussion around px, em, and rem. I’ve found that the biggest challenge when moving from fixed px values to scalable rem units is doing the conversions consistently across a stylesheet. A px to rem converter can make that process much quicker, and having a rem to px converter is useful when you need to work backward or verify existing values. I’ve been using this https://www.utilityforweb.com/px-to-rem/ tool for quick two-way conversions while working on responsive layouts.