Savings Rate & FIRE Tracker

The number this is built around

Almost every question about retiring early collapses into one variable, and it is not your salary, your fund selection, or your ability to time a market. It is the share of your take-home pay you do not spend.

The reason is that a savings rate works on both ends of the problem simultaneously. Every extra point saved is a point more going into the portfolio, and it is also a point less of spending that the portfolio will eventually have to support for the rest of your life. One lever, two effects, pulling in the same direction. That is why the relationship is so violently non-linear.

This table is built into the tracker and recalculates against whatever return assumption you enter, so you can see how sensitive the whole exercise is to that one input. The full argument lives in Your savings rate is the whole game.

What is in the workbook

Four tabs. Two you fill in, two that do the work.

• Start Here. Version, instructions, a legend telling you which cells to touch, and the disclaimer.
• Assumptions. Your target portfolio, withdrawal rate, current invested assets, age, target age, and expected real return. Every projection in the file traces back to these six cells.
• Monthly Log. Twelve rows. Gross income, taxes and deductions, spending, and dollars invested. Take-home and savings rate calculate themselves.
• Dashboard. Savings rate to date, progress to target, your own number derived from your actual spending, years to independence at your current pace, the age that lands on, and your coast number.

Yellow cells with blue text are yours to edit. Everything else is a live formula. Nothing in the file is a number typed in by hand, which means you can change any assumption and watch the whole thing move.

How savings rate is defined here, and why that matters

The tracker divides dollars invested by take-home pay. That is a choice, not a law, and you should know what the alternatives do to the figure.

Using gross income as the denominator gives you a lower number, because it counts taxes as spending. Counting your employer match as savings gives you a higher number. Some people include mortgage principal payments, which is defensible since it builds equity, and some exclude them, which is also defensible since a house you live in does not fund your retirement. Every version has a case.

What does not have a case is switching between them. A savings rate is useful as a trend, and a trend requires the same measuring stick month after month. Pick a definition, write it on the Start Here tab, and stop relitigating it.

The workbook also logs spending as its own column rather than deriving it from take-home minus invested. That is deliberate. The gap between what you had left and what you actually put to work is where most of the money quietly goes, and a sheet that derives spending will hide that gap from you forever.

The coast number

The Dashboard reports a coast figure: the amount you would need invested today for compounding alone to reach your target by your chosen age, contributing nothing further. It is worth tracking because it arrives decades before independence itself and it changes what your job is for.

One reconciliation worth flagging, since it trips people up. The coast FIRE essay quotes $93,663 for a 30-year-old targeting $1,000,000 at 65, using a 7% nominal return. This spreadsheet defaults to a 5% real return instead, so its coast figures look larger. They are not disagreeing. One is measured in future dollars and the other in today's dollars, and the second is the more honest unit when the horizon is thirty years long. Enter 7% on the Assumptions tab and the essay's number reappears exactly.

What this tool cannot tell you

A single expected return is the largest simplification in the file, and it is worth being blunt about the cost. Real markets do not deliver an average every year. They deliver a sequence, and the order the returns arrive in matters nearly as much as the average itself, particularly in the years immediately around the day you stop earning. A bad decade at the start of retirement and a bad decade at the end produce very different outcomes from identical average returns. No straight-line projection captures that, including this one.

The tracker also ignores taxes on withdrawal, healthcare before Medicare eligibility, Social Security, changes in spending over a long retirement, and the fact that a 4% withdrawal rate is a historical starting point rather than a guarantee. The field guide entry on the FI number covers where that rule came from and where it strains.

Treat every date this sheet produces as a direction, not a plan. Its real value is comparative: it tells you what raising your savings rate five points does to your timeline, which is a question it answers honestly.

Using it

Set the Assumptions tab once. Log one row a month, which takes about five minutes if you have a banking app. Read the Dashboard whenever you feel like it, and ignore it the rest of the time. In January, copy the file, rename it for the new year, and start fresh. Keep the old ones, because after three or four years the trend across them is more useful than any single dashboard.

Found an error, or think a definition here is wrong? Tell me. Corrections get published with a date attached, the same as they do for the research reports.