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The basics
An income or spending amount is only the starting point. Its dates say when it applies; its change-over-time setting says how it grows or shrinks.
Use separate stretches for distinct phases, such as full-time work followed by part-time work, or travel spending that falls later in retirement.
Illustrative numbers
Two meanings of a $12,000 budget
Starting annual budget$12,000
Flat dollars one year later$12,000
Tracking 3% inflation one year later$12,360
Both begin at the same amount. Only the inflation-linked budget keeps the same purchasing power in this example.
Calculation transparency
How it works in MoneyWhatIf
- 01
Change modes include flat dollars, inflation-linked amounts, increases or decreases, and custom curves. Read whether a selected rate is an absolute change or an adjustment relative to inflation.
- 02
Custom curves interpolate the rate between the points you set. They describe changing rates, not a list of account balances or future spending totals.
- 03
A date can follow a calendar point, an owner’s retirement, or a life milestone where the field supports it. Partial years use the months covered by that range.
- 04
When ranges overlap, the earlier range has first claim on the overlapping months. Adjacent ranges are easier to review than overlapping ones.
Keep in mind
Model limits
Annual charts summarize the months inside each year; they do not show a daily cash ledger.
A change in the chart’s Today’s money switch changes the display. It does not change the entry’s inflation or growth settings.
This explanation documents the planning model. It is educational, not individualized tax, legal, Medicare, or investment advice.
Where it appears
Where to use it
See this concept in context, with a guide to each page and its controls.
The words behind it
Related financial terms
Plain-English definitions, with 2026 figures and worked examples, from the financial terms glossary.