Hi Alexsei
My name is Elliott Dobbs and I'm the founder of SketchAndCalc.com
I'm grateful for the mention here on DansDeals. You mention you had difficulty getting the numbers to match the plans, and I wanted to offer some advice.
SketchAndCalc uses pure coordinate geometry math to calculate area, so it's possible the plan isn't to perfect scale. Once you have the rough shape you can adjust each line length to match the plan in two ways:
1. Manually, by clicking a vertex and adjust it's position using your keyboards cursor keys until the number match the plan.
2. Automatically, by clicking a length label and entering in the value. You'll note that once the label is selected it points to the vertex that will move when entering in a new value. Clicking again toggles between vertices.
It's worth pointing out that setting the drawing scale when you import is important, by drawing a known length as accurately as possible. I'd recommend nominating the longest length when setting the drawing scale. Anyway, I hope these tips prove helpful, I've added a 1 minute video intro below.
Cheers
Elliott