How NextGen computes

What is computed

Two runs of the same plan up to the eighteenth birthday: one begun at birth, one begun at the age you set. The picture shows the first run, and what waiting costs is the gap between the two.

The monthly amount is paid in at the start of the month. Interest is credited once a year, because the series behind the assumption has one value per year.

• Once a year. Each of these is paid once a year, at the start of the year.
• A single amount at the start. Paid when the plan begins. In the run from birth that is the birth itself.
• Yearly rise of the monthly amount. Raises the monthly amount at the start of every year. The amounts given once a year stay as you entered them, because a birthday gift is decided again every year by whoever gives it.

Where the figure comes from

The dial starts on the S&P 500 over the last 20 years. Every mark on it is listed below with its class, its source and the day it was read. Between two marks the figure is your own assumption.

• The figure is the average yearly return of the index with dividends reinvested, worked out from its year-end values for 2005 and 2025.
• The return of the S&P 500 is measured in US dollars.
• The exchange rate, product costs and taxes are not included.
• Past returns are not a forecast.
• S&P 500: Aswath Damodaran, NYU Stern. Covers up to 2025, fetched 9 November 2026.

Set by you here. Nobody published this figure, and it is not a forecast.

What waiting costs

The three cards are the same plan begun today, in three years and in five years, each carried to the eighteenth birthday. The second line of a card is its distance to the first card. The sentence under the picture gives the cost of waiting as a share of the run from birth.

The run from birth stays in the picture for comparison, whatever you set here.

Three things Pro adds

The Pro figures are computed on the server with the same arithmetic as the simulation tab. For the runs, the amounts given once a year are counted as a twelfth every month, which is why the band and the picture can differ slightly over eighteen years.

• In nine out of ten of the 2,000 runs at least. The same plan run 2,000 times, with the ups and downs of the single years drawn at random, so the figure above has a range around it and not only one line.
• Left after product costs, taxes and inflation. Pro takes product costs, taxes and inflation off the result for your country. A child has a tax allowance of its own, and whether it applies depends on whose account the money sits in and what else the child receives. This page does arithmetic and gives no tax advice.
• Year by year. Pro shows every one of the years as a row, with what was paid in and what the simulation says.

What is saved

Nothing is saved. No name, no date of birth. The age is enough.

What every figure is counted in

The line under every result says it in keywords: nominal · before costs and taxes · past returns are not a forecast

• Nominal. An amount counted in the money of the year it falls in, with nothing taken off for rising prices. It is the figure that would be in the account.
• before costs and taxes. The exchange rate, product costs and taxes are not included.
• past returns are not a forecast. Past returns are not a forecast.

Sources, with the day they were fetched

Every line names the publisher, the last year the series covers and the day the figures were last fetched. The full list of every source in the product is on the sources page.

• Consumer prices, United States: US Bureau of Labor Statistics, CPI-U, all items, US city average (CUUR0000SA0), annual averages. Covers up to 2025, fetched 2026-09. Source
• S&P 500: S&P 500 total return, Aswath Damodaran, NYU Stern. Covers up to 2025, fetched 2026-10-22. Source

All sources