Individual measurement can never be correct.

Well, I think if you’re already making an offer based on measurement, then it should at least be transparent. I only know measurements including details about corners/rebates and not just rough estimates. If it’s stated like that in the DIN, the rough estimate may be correct (and the invoice will then be created in detail), but who reads a DIN as a layperson? A note in advance or on the offer would be nice then.

The contractor responded correctly to the OP’s question and explained how his calculation is structured. It is even DIN compliant and quite common.
Of course, you can make it more detailed. But who really wants to invoice every edge and every rebate separately in the end?
The calculation will probably come to at least the same result.

Or more expensive because due to the increased effort of the offer calculation, he has to raise the overhead cost key. Blessed are the simple-minded, for they own the cheap offer!

Hello,

so approximately 62m² are overmeasured. 62m² / 2.5m² = at least 25 openings! Impressive effort to measure everything precisely in a first short offer.

Creating offers according to [DIN] is absolutely common. But maybe you will find another company that breaks down all the reveals in the offer to the millimeter exactly.

so about 62m² are overmeasured. 62m² / 2.5m² = at least 25 openings! Impressive performance to measure everything exactly in a first brief offer.

Every interior door has two sides (2*2m² per door), so it even seems rather little to me.

A note in advance or on the offer would be nice then.

What do you mean ? The craftsman should have the entire VOB on the offer, right? Or recite the craftsmen regulations before entering the construction site during a chat? ;) It was simply misunderstood by the OP. That's it! But probably the misunderstanding would not have occurred at all if the craftsman, who rarely gets a request from an end customer, had a construction manager or architect as a contracting party or their expert as the client.

Milkmaid's calculation: I choose where I refuel. They all have different prices, sometimes even a 10% difference.

What does the price have to do with it? It was a figurative comparison; refueling 20 liters and paying for 40 liters surely has nothing to do with price differences.

That's how it is! The "gaps," meaning what you deducted, remain to factor in the edge effort..

The reveals and lintels are additionally calculated in linear meters. So I am paying twice.

You are free to take someone else. There isn’t much more to say. If the price is not pleasing, go to the next store or request a new quote.

This is not about the price yet but about the incomprehensible measurement.

Overmeasuring 220 sqm and "precisely billing" 158 sqm is practically the same. Where there are openings, reveals are added – it doesn’t exactly compensate 1:1, but who would really want that if the quote letter were more expensive than the actual work?

Reveals and lintels are additionally billed in linear meters.