Guide

Which assumption does the answer depend on?

A savings projection is one number built on five guesses. The useful question is which of the five it is standing on.

One number, five guesses

What a starting sum and a monthly amount come to depends on the return they earn, the inflation that eats into it, how much really goes in each month, for how many years, and what there was to begin with. A chart shows the result and none of that. Two plans that look identical can be very different: one survives a point off the return, the other falls apart on it.

Moved one at a time, by an amount you can see

The calculator below moves each of the five alone — the return two points either way, inflation one point, the monthly amount a fifth, the years three and the starting sum a tenth — holds the rest, and ranks them by how far the answer moves. The amounts are printed on every row, because the order is a statement about them: move the return by a quarter of a point instead and it drops down the list. A ranking whose steps you cannot see is a choice presented as a finding.

Why it is measured in today's prices

Inflation does not change the number on a statement; it changes what that number buys. Measured in cash of the day, inflation would come last with a swing of nothing — the one conclusion that is certainly false. In today's prices it takes the place it actually has.

What one at a time cannot show

Two assumptions going wrong together can be worse than either alone, and moving them one at a time does not show that. The app's own projection is a different instrument: it runs hundreds of possible futures, with returns and exchange rates varying from run to run while inflation follows its set path, and reports a range. On its Future screen, What this rests on does this same test on your own figures.

No tax, and no charges, are modelled here, and the return is one steady figure every year. Nothing here says which assumption is right, or what anybody should assume.

Try it

Everything you type here stays in this browser. Nothing is uploaded, nothing is saved, and no account is needed. The same calculator can go on your own site — see the widgets.

About Valnivo

Valnivo is a free financial planning tool that projects your income, spending and savings over 10, 20 and 30 years. It handles money held in several countries and currencies, and it is private by default.

It holds no money, connects to no bank and never asks for banking credentials. Every figure it shows is an illustration built on your own assumptions, not a forecast and not advice. Open the app.