In Matthew 18:21-35, Jesus told a parable to illustrate the principle that we should forgive others. The perspective we need is how much God has forgiven us.
So how big is God's gift of forgiveness to us, then?
The man who was forgiven by the king in verse 24 was in debt to the tune of 10,000 talents.
The footnote in my ESV Bible says that "a talent was a monetary unit worth about twenty years' wages for a labourer". To try and convert that into today's terms, a year's wages for a labourer would be somewhere between £10,000 and £20,000, probably. Depends on the labourer, the skill level, how much they're in demand. Take the bottom estimate, and say that any labourer today certainly should be paid in excess of £10k.
So one talent is 20x that amount = £200,000.
This man owed 10,000 talents = £2,000,000,000 = £2bn (for the British reader). At current exchange rates, that's $3.23bn in US Dollars.
According to Forbes' attempts to list the billionaires around the world, there are exactly 9 individuals in the United Kingdom who possess that sized sum. So, David and Frederick Barclay, owners of the Ritz and Cavendish hotels, do have that sized sum (just). However Ian and Richard Livingstone, traders in real estate, do not.
Quite how the king's servant managed to run up debts the size of the GDP of Togo is not told to us in Jesus' story. What is clear is that he had had the most enormous debt wiped out overnight. He certainly would never have paid it back.
And that is a picture of the magnitude of God's forgiveness of our sins. If we find it hard to forgive others, is it in part because we haven't really grasped the scale of our own forgiveness?