What does the UK, France and the Netherlands have in common?

[Sarmatian]

I'm not confident that it could be gotten to within several orders of magnitude...

China and Japan would need to pay as well, btw.

It's not a good idea to siphon billions - who knows, maybe trillions - from the richest and give to the poorest, especially when the ultimate cost might leave the former indebted for centuries at least.

At the minimum, any countries awarded reparations should have a share of the settlement awarded directly to each adult citizen, and nothing at all to the national government itself.

Anyway, let's invoke statute of limitations.

Calculating the actual amount would be the hardest part. Modern day USA, Canada and Australia were sparsely populated with almost non-existent economies, except some barter and practically no concept of ownership. Some parts of Africa were similar.

India or Dutch colonies in southeast Asia on the other hand had functioning states and economies. If it were to be calculated on the value on actual goods, adjusted for inflation, just the worth of salt from India, a tax that went directly to the British crown would be enough to bankrupt UK several times over. If we try to add other, direct and indirect profits, we would probably come to some unimaginable figures.

Bankrupting those nations and throwing world's economy in a turmoil obviously isn't the solution.

What I think is fair is actually a compromise - we couldn't really take the price of pepper in 15th and 16th century when 1kg of pepper = 1kg of gold as a starting point. Likewise, it wouldn't be fair to base the calculations on the 21st century price of pepper. Some middle ground would have to be found.
It also wouldn't be fair to expect former colonial masters to "pay up" immediately. Maybe former colonial countries could set up very long term funds for development of their former colonies. Money from those funds would be used to build infrastructure, highways, railways, ports, airports, schools, university, hospital, housing etc... in former colonies and companies from the former colony and former colonial country would have preferential status to be picked. So, for example, in the case of India, British and Indian companies would have "first option" to build a highway in India. If they can't do it or don't want to do it under allotted budget for whatever reason, only then are other international companies offered to do it.

That way there would be less corruption than with cash payments, former colonial countries could bear it relatively painlessly, former colonies get infrastructure developed for free and the money is injected, at least partially, into the former colonial country economy.