There's one phrase that's been getting a real work-out ever since Labor's election win in May.

The treasurer and finance minister have both made plenty of references to the "trillion dollar debt" weighing down the budget they inherited.

It has helped build a case for restrained spending and budget repair, offered as a key reason why the government cannot take up all sorts of ideas.

One trillion dollars is undoubtedly a very large amount of money.

But by global standards, it's not an unusually large debt — or even a particularly remarkable figure.

And it's not quite a trillion dollars, either.

So how big is the national debt?

At the end of July, the total size of Australia's national debt was $895 billion.

That's about $100 billion short a trillion dollars.

But many economists argue the total, or gross debt figure is not the best debt figure to look at.

They point to the net debt figure, which takes the total debt then subtracts many of the government's financial assets — like cash it holds, deposits and loans it is owed.

That figure is substantially lower, at $515 billion, or just over half a trillion dollars.

Which is still a huge amount of money. But economists also look to another key indicator.

They compare the size of the debt, to the size of Australia's economy.

Net debt is currently at 22.5 per cent of GDP, or just over a fifth of Australia's total national income.

Gross debt is obviously higher, at closer to 40 per cent.

It's a big debt, but it's not the biggest

Comparing debt to GDP allows Australia's debt to be put in a global context, too.

And the comparisons are actually pretty good.

Australia's gross debt-to-GDP is below average in the OECD, which is basically a collection of wealthy countries.

Countries like the UK and US are carrying debts larger than their economy.

Economist Sarah Hunter from KPMG said the numbers reflect pretty favourably on Australia.

"We're still at relatively low levels [of debt]," she said.

"When I look internationally, if you drill down and compare across developed economies who are similar to Australia, then that's very much the case.

A growing bill

Crises are expensive, and the past two decades have served up a few.

And a quick look at Australia's debt levels lays out just what the bill looks like.

Heading into the global financial crisis in 2008, Australia's net debt was in negative territory — the government was owed more than it had borrowed.

But the response to that economic crisis came with a significant price, as debt levels jumped to $200 billion by 2013-14.

The government changed hands in 2013, and net debt kept climbing.

Another crisis arrived in early 2020 as the pandemic hit, pushing net debt to a high point just shy of $600 billion, a touch under 30 per cent of GDP.

Economist Chris Richardson said those sorts of situations are when debt is perhaps most useful — allowing governments to intervene, and prevent more serious economic trouble down the track.

"Debt rose very fast with the cost of fighting the war against COVID," he said.

"Although Australia did throw a lot of dollars at COVID — more than some other nations did relative to the size of our economy — it also worked better here.

"Partly because we got a good public health result, our economy rebounded earlier than others did.

How big a problem is the debt?

There are plenty of opinions about how much debt is too much debt.

One of the bigger issues the government faces is the cost of the repayments.

Jim Chalmers has already outlined interest payments on debt as one of the five fastest-growing budget pressures facing the government, along with defence, the NDIS, aged care and health.

As households face rising interest costs on mortgages, so too does the government face rising interest bills on its borrowings.

Many economists agree Australia's debt is nowhere near crisis levels, and despite frequently pointing to the size of the debt, so does the government.