Takeoff Studio - free
Take voids, columns and stair openings out of an area. Lay joists, studs or posts at set centres and get the count and the total length. Multiply a measurement for repeated rooms, and turn a roof measured on plan into its true area. All free.

Select an area, rectangle or circle and choose Add cutout. Draw the hole inside it, or press B for a rectangle. The quantity becomes net everywhere - labels, totals and exports.
By default the perimeter is the outer edge, for skirting or edge trims. Tick Perimeter includes cutout edges to add the edges of the holes, for nosings or upstands round a void.
Choose Spacing (J), pick Along a line or Across an area and type the centres - 400, 0.6 m, 16" or 2' all work. You get the count and, across an area, the total member length.
Set Times on any measurement for repeated rooms or floors, and Slope on a roof or ramp measured on plan - in degrees (30), as a ratio (1:2) or a percentage (15%).

Help: Measuring extras has every option in detail.
Free in Takeoff Studio. Measuring is free and always will be - no time limit, no account. Takeoff Studio Pro is there if you want to price and export your takeoffs.
The true quantity is the plan quantity divided by cos(slope). Apply slope only to lengths that run up the slope; perimeters aren't slope-corrected.
Times is positive only. Use Deduction for a negative quantity - the two work together.
Yes. Change the centres, ends or direction in the Selection tab, or drag the points, and the count updates straight away.
Yes. Cutouts move, copy and copy to other pages with their area, and volume uses the net area.
Yes. Cutouts, Spacing, Times and Slope are all free in Takeoff Studio.

Click inside a room and it's traced to the walls. Auto walls measures walls on CAD drawings.

Floor, ceiling, wall and skirting quantities for every room, with totals per finish and level.

One measurement becomes every item it needs. Then an Excel bill in NRM2 order with live formulas.

Lay the new issue over the old one. Every change is boxed, listed and ready to cloud.

Box one socket or light and every match is found and ringed for you to check.

Scale from the title block, scale regions, the drawing register and text search.
Measuring is free. Takeoff Studio Pro is £24.99 a month or £199.99 a year, and the first month is free.