A retirement planner that shows its working

Glidepath is a free, open-source desktop app for planning retirement and investments, built UK-first. Every number in your plan is a fact you stated, a decision you made, or an assumption the app defaulted — always inspectable, never silently guessed.

All data stays local on your machine; nothing is transmitted.

Get Glidepath View on GitHub
The charts tab: the Monte Carlo fan chart — nested percentile bands deepening toward the median line — beside the success-rate readout and the retirement-age and backtest cards

Facts, decisions, assumptions

The core principle: you can always see where a number came from. A provenance view lists everything each projection used — with its value, source, date, and whether it was defaulted or overridden.

Fact

What you stated

Your date of birth, salary, balances, pension forecasts. Entered by you, dated, and never altered by the app.

Decision

What you chose

Retirement age, contributions, planned outflows. The only fields a what-if scenario is allowed to override.

Assumption

What was estimated

Returns, inflation, longevity, uprating policy. Each carries its value, source and date — and you can override any of them.

What it models

UK, single or couple, from verified 2026/27 tax-year data files — policy figures are never hardcoded.

Tax wrappers

Workplace DC, SIPP, S&S ISA, LISA, GIA and cash — with UK contribution-relief mechanics and dividend and savings taxation.

DB & state pension

Deferred or actively accruing CARE-style defined benefit pensions with revaluation, early/late factors and commutation; state pension from your official DWP forecast, including deferral.

UK tax, verified

rUK and Scottish income tax, pension annual allowance with taper and MPAA, and the lump-sum allowance — all from dated, sourced data files.

Couples

An optional partner, modelled end to end: pooled household decumulation with each person taxed individually, the marriage allowance, survivor modelling, and joint-life annuities.

Monte Carlo projection

Deterministic or Monte Carlo runs: success rate, probability of ruin, ending-pot percentiles and a probability fan chart — reproducible from a seed, with a de-risking glide path and tax-aware decumulation.

“When can I retire?”

A solver for the earliest retirement age that sustains a target income — a replacement rate you choose, met deterministically or at a Monte Carlo success target.

Historical backtesting

Replays your plan over every rolling window of world market history since 1900 — sequence-of-returns risk that independent Monte Carlo draws miss.

Scenarios

Named what-ifs over your decisions and assumptions, compared side-by-side. Plans are saved as a local JSON file you own.

Local and private

A desktop app, not a web service. Your plan lives in a file wherever you choose, and nothing ever leaves your machine.

A closer look

All screenshots show example data, not anyone's real finances.

The facts tab: the About you, Household spending, and State pension cards of the entry form, with the example plan's values filled in
Facts entry — everything on this screen is either a fact you state or a choice you make; anything estimated lives in the assumptions inspector instead.
The stated-vs-assumed tab: tables of stated facts, choices in effect, assumptions used with sources, and the plan structure
Stated vs assumed — the provenance view: the facts you stated, the choices in effect, and every assumption the run used with its value, default/overridden status, source, and date.

Get started

On Windows x64, download one file and run it. Python and terminal commands are not required.

Windows: download and run

Windows executables are available in releases from v1.1.0.

Windows downloads →

  1. Open the latest release and look under Assets.
  2. Download glidepath-X.Y.Z-windows-x64.exe.
  3. Keep it in a folder of your choice and double-click to launch.

The file is the app itself; there is no installation wizard. To upgrade, close Glidepath and download the newer executable. Your saved plans stay where you put them.

The app is not yet signed with a Windows publisher certificate. Windows may show “Windows protected your PC” or “unrecognised app”. Check that your download came from this repository’s release before deciding whether to proceed.

If the latest release has no .exe yet, use the uv installation below.

Install with uv — Linux, macOS or Windows

uv installs Glidepath from PyPI and fetches the Python it needs. On macOS or Linux:

$ curl -LsSf https://astral.sh/uv/install.sh | sh

Close and reopen the terminal, then install and launch Glidepath:

$ uv tool install glidepath
$ glidepath

For Windows PowerShell commands and terminal setup, follow the uv installation instructions. Upgrade later with uv tool upgrade glidepath.

The getting-started guide walks through what to gather, entering it, reading the projection, and changing the assumptions behind it. pipx install glidepath works too. Or run straight from a checkout: uv run glidepath installs the locked dependencies on first run.

The app launches with an example plan already projected, so every tab has something to show — replace its values with your own facts, or clear the form and start blank. Save your plan from the File menu as a .glidepath.json file stored wherever you choose; the next launch reopens it automatically.

Disclaimer. Glidepath is a personal modelling tool for exploring retirement scenarios. It is not financial advice and is not regulated; its outputs depend on assumptions that will not match reality. Do not make financial decisions based solely on this tool.