How much can I actually spend today?

Most people check their bank balance and guess. The balance is a real number, honestly reported, and it is almost never the answer to the question you are actually asking, which is:

If I spend money today, will something break later?

The balance cannot answer that, because it does not know what is coming. Rent has not left yet. Neither has the phone bill, or the card payment, or the four days of groceries between now and payday. All of that is already spoken for. It is sitting in the same number.

Here is the arithmetic that does answer it.

Start with what you can actually reach

Not net worth. Not your savings. The money in the accounts you spend from, today.

If you have several checking accounts, add them up. Leave investments out. Leave anything with a withdrawal penalty out. This is the money that can pay for a sandwich this afternoon.

Checking                                    $1,790

Take out the part that is not for spending

Almost everyone has a floor they do not want to go under. Call it a buffer. If you have never picked one, pick one now, and pick it deliberately rather than discovering it at 2am.

The exact figure matters less than the fact that it is decided in advance. A buffer you choose while calm is worth more than one you negotiate with yourself in a store.

Checking                                    $1,790
Buffer, kept where it is                     −$400
                                        ───────────
Spendable cash                              $1,390

Take out everything already committed before payday

This is the step people skip, and it is the step that does all the work.

List every outflow you already know about between now and your next paycheck. Not a typical month. The actual ones, with actual dates:

Rent, lands Wednesday                        −$950
Phone bill, Friday                           −$143
Card minimum, due Monday                      −$57
                                        ───────────
Left for the days ahead                       $240

Two things trip people here.

Card payments are not the same as card spending. What you owe the card is one number. What will actually leave your checking account before payday is another, and it is the second one that belongs on this list. If you pay the minimum, put the minimum. If you clear the statement in full, put the statement balance.

Annual bills still count. Insurance that lands once a year still lands. If it falls before your next payday, it goes on the list at full price.

Divide by the days you actually have

Not thirty. Not "the rest of the month". The number of days until money next arrives.

$240 over the six days to payday            = $40/day

That is the number. Forty dollars today, and if you spend forty dollars today you will still make rent, still pay the phone bill, still cover the card, and still have your buffer intact when the next paycheck lands.

Spend sixty today and you have not broken anything. You have borrowed eight dollars a day from each of the five days that follow. That is worth knowing at the register, and it is the whole reason the number is useful: it converts a vague unease into an exchange rate.

Doing it on paper

You can run this by hand and it works. Once a week, on the same day:

1. Write down your checking account balances.
2. Subtract your buffer.
3. List every bill and card payment due before your next payday, with dates. Subtract the total.
4. Divide by the number of days until payday.

Fifteen minutes, and you will be more accurate about your own money than most budgeting spreadsheets manage.

Why it stops working

It stops working for the same reason every manual system stops working, which is not laziness.

The inputs move. A direct debit changes amount. A subscription you forgot renews. Your employer pays on the last working day, so a weekend shifts payday. A refund lands. A card statement closes and the minimum changes. Every one of those quietly invalidates the number you wrote down on Sunday, and nothing tells you.

So by Thursday you are working from a figure that was true four days ago, and the only way to know that is to do the whole thing again.

That is the actual job. Not the arithmetic, which is simple, but the watching: noticing that one of about forty inputs moved, and redoing the sum before you make a decision on a stale answer.

What Ralphy does with this

Ralphy runs exactly the arithmetic above, every morning, against your real accounts. Same four steps, same order.

The difference is that it re-runs when an input moves rather than when you remember. A bill changes amount, a paycheck lands early, a card posts, and the number is different before you next look at it.

And it shows the working. Every figure opens into the receipt it came from, so you can see which bill, on which date, for how much. If one is wrong you correct it, and the correction sticks.

The number is advice, not a rule. Nothing is blocked, nothing is held, and going over it is information rather than a failure. You can try a morning of it in your browser without installing anything or connecting a bank.

The arithmetic is not the hard part. Keeping it true is.