What did one unit really cost you?

How the tool calculates

The average cost is a weighted mean, not a plain average of the prices. The calculator adds up every purchase amount (quantity times price) and every purchase fee, then divides the result by the total quantity. Buy a lot at a high price and a little at a low one and you land closer to the high price. Two purchases, 0.05 units for 39,000 euro and 0.03 units for 56,000 euro, come to 0.08 units and 3,630 euro, here calculated without fees, so an average cost of 45,375 euro per unit. The mean of the two prices would be 47,500 euro and would be wrong.

The break-even price sits above that, because something is taken off again on the sale. The formula is average cost divided by (1 minus the selling fee). At a selling fee of 0.5 per cent and an average cost of 45,375 euro, break-even is 45,603 euro. The slider assumes a price between 20 and 300 per cent of today’s market price and recalculates value and result. That is an assumption to play through, not a forecast and not a statement about where a price is going.

Why tax works differently

The rules in this section are German tax rules and apply to private investors taxed in Germany; readers taxed in another country are governed by that country’s rules. For your own overview the average is handy, but the tax office does not take it that way. The circular of the German Federal Ministry of Finance of 6 March 2025 on crypto-assets names individual identification first, in paragraph 61: anyone who knows which units they sold calculates with the acquisition costs of those units. Where that is not possible, the units acquired first count as sold for the holding period; for valuation the average method is provided for, and for simplicity first in, first out may be used there as well. The qualification matters: the assessment is made per wallet, and the method once chosen stays until every unit of that label in that wallet has been sold.

In practice that means a partial sale usually hits the oldest units. Those are often the ones held for more than a year and therefore tax free under section 23(1) sentence 1 no. 2 of the German Income Tax Act (Einkommensteuergesetz), while the more recent purchases are still inside the period. The purchase fees are not lost in this; they simply run through a different item than the selling fees. Transaction fees on purchase are counted by the ministry circular as incidental acquisition costs, while transaction fees incurred in connection with the disposal are to be treated as income-related expenses under paragraph 59. Both reduce the taxable gain, which section 23(3) sentence 1 of the German Income Tax Act defines as the disposal proceeds less acquisition costs and income-related expenses.

The costs that are not on the invoice

Next to the fee that is shown sits the spread, the gap between the buying and the selling price. It never appears as a line item, but it works like a second fee: sell again straight after buying and you get back less than you paid, even with no stated fees at all. That is why this calculator has two separate fields, one for the purchase fee on each purchase and one for the selling fee in per cent. If you want to include the spread, add it to the selling fee.

That these figures are worth checking yourself is shown by a survey from BaFin, the German financial supervisory authority. After a representative survey of 1,000 people in April 2026, around 13 per cent of adults in Germany hold crypto-assets, which is more than nine million people. Across 16 knowledge questions, holders answered 57 per cent correctly and 31 per cent wrongly. Knowing your own average cost is at least one number out of the fog.

Where the calculator stops

It knows only purchases, not sales. If you have already sold part of a holding, you have to take the sold quantity out of the rows yourself, otherwise the total quantity is wrong. It calculates everything in euro and assumes the purchases were settled in euro. A swap of one coin for another counts as a sale and a purchase at the same time; here it can only be shown as a purchase at the price on the day of the swap. Staking rewards, airdrops and mining rewards are acquisitions in their own right at the market price when they accrue, so they belong in the list with that price and not as a fee. The market price comes from a file on this site that is rewritten every ten minutes, and the price you actually sell at will differ. And the calculator says nothing about whether a purchase or a sale is a good idea.

Frequently asked questions

Sources