Floor 3 · Forecast

The next 12 months

A Kalman filter reads a made-up ledger of 36 months, learns its level, its trend and its yearly rhythm, and projects the cash balance 12 months ahead: an expected path, 1σ and 2σ bands, and the chance of dipping under a floor you set.

This demo runs in your browser. The ledger is a sample file on this site; what you type stays on this page and nothing is stored.

Not yet releasedThe app's forecast runs the same filter on-device, and every number comes from the engine, never from a language model. It is not in the build our testers have today, and we don't promise a date.

The demo

Try it on the sample ledger

Change an input and the forecast updates. Income and the loan payment shift every future month by the difference from the ledger's $4,100 and $450; the floor and the goal change which probabilities are shown, nothing else. The numbers are illustrative.

Loading the sample ledger…

Sample data Dots are the ledger's month-end balances; the thin line is what the filter believed each month; the dashed line is the expected path ahead, inside its 1σ and 2σ bands.

Month-end balance (ledger)
Filtered level + season
Expected balance ahead
1σ band (about 68 %)
2σ band (about 95 %)
Floor
Goal

Next month

Expected balance, next month: —
One standard deviation (1σ): —
2σ range (about 95 % of the outcomes): —

The twelve months

Lowest expected month: —
Highest chance of dipping under the floor: —
Chance of being at or above the goal in the last month: —
Trend the filter found: —
Your what-if shift: —

Month by month: the expected balance, its spread and the two probabilities
Month	Expected balance	1σ	2σ range	Chance under the floor	Chance at or above the goal
The rows fill in once the demo runs.

Show the math

The substituted equations appear here once the demo runs.

Example Computed from the sample ledger and your inputs. Φ is the standard normal cumulative distribution; the noise values are the demo's fixed settings, not estimates.

Plain terms

What this page is

The numbers are illustrative. The ledger is made up, the noise settings are chosen by hand, and the output describes that sample, not any person. We publish no accuracy figure for the forecast.
It is not financial advice. A probability on this page is a property of a model; it is not a recommendation to save, borrow or spend.
The model is simple on purpose. It is linear, its noise is Gaussian, and its spread grows by a fixed rule. Real months have one-off events that no twelve-month rhythm predicts; those land in the noise and in the width of the bands.
Everything here runs in your browser. The page loads one sample file and computes with it. Nothing you type is sent anywhere, and this site keeps no record of it.
In the app: in construction. The app's forecast runs the same filter on-device, and every number comes from the engine, never from a language model. It isn't in the build our testers have today, and we don't promise a date.
Research, separately. A quantum amplitude-estimation cross-check of the shortfall probability, never run on this page or in the app, is part of our research lane. It is research, nothing more: nothing here touches a quantum computer.

Source for the method: the Kalman filter and the basic structural time-series model (local linear trend with a dummy seasonal), as in standard time-series texts; the formulas are printed above so they can be checked.

The input

The sample ledger

Thirty-six months for one made-up household. Net income is $4,100 a month. Housing is $1,450, the loan payment $450, the car $310, phone and insurance $190; groceries, utilities, fuel and everyday spending vary a little month to month. A few lines repeat each year: gifts in December ($650), travel in July ($420), school costs in August ($260), taxes in March ($180) and an after-holiday month in January ($120). Four repairs land in fixed months. The balance starts at $2,400.

No real person, bank or merchant is behind it. The file is forecast-ledger.json, and the same file feeds the demo above.

The thirty-six months

Month-end balance = last balance + income − spending
Month	Income	Spending	Net	End balance
The rows fill in once the ledger loads; the file above holds every line.

The roof

The math is one tap away, every time

Every figure in the app is computed by its own engine, with the equation beside it. This forecast will be built the same way.

Get SI Money Tracker Coming soon

The budget comes with the app, no account needed. Plus adds bank connection and automatic import: 7 days free when Apple says you're eligible, then $9.99/month, billed through your Apple Account. Cancel anytime in Settings.