You want to retire at 50. Your Tiller sheet shows every penny. It still does not show the date. Here is what is missing.
Tiller does not do FIRE projections out of the box. The default templates track monthly cash flow and category spend. To get a FIRE number and a date, you would need to add a separate sheet with formulas for compounding, withdrawal rate, and the State Pension income from 67. It is doable. It is also the kind of work most people start and never finish.
Delphina gives you the number and the date on day one. The 25x multiplier, the State Pension inclusion, and the projection forward are all built in. The monthly savings rate feeds the projection automatically because the same connection that powers the budget powers the planning.
Tiller gives you the data foundation for any model you want to build. If you enjoy writing Google Sheets formulas and you want to stress test your own assumptions against historical US market returns, Tiller is the right starting point. You can build a projection that matches exactly how you think about sequence-of-returns risk and inflation.
Tiller is also useful for sanity-checking any answer Delphina gives you. If you want to know what happens if your returns are 3% real instead of 5%, you can build both scenarios in your spreadsheet and compare. The transparency of seeing the formula is worth the work for some people.
Delphina gives you a date you can act on. A UK saver with £180,000 across pensions and ISAs, spending £3,200 a month and saving £1,800 a month, gets a specific answer: you reach 25x your spending at age 54 and 7 months. The State Pension from 67 reduces the required portfolio by around £314,000, which moves the date earlier.
Delphina also shows you what changes the date. Increasing your SIPP contribution by £300 a month brings retirement forward by 8 months. Reducing monthly eating out by £150 adds 3 months. You can adjust the levers and watch the projection update in real time, which is the part Tiller cannot do without significant formula work.
Multiply your real annual spending for the last 12 months by 25. That is your FIRE number today, with no tool. Connect Delphina this week to get the date. If you have a Tiller sheet you want to keep, the two can coexist: Tiller for the data, Delphina for the plan.