How much are you overpaying by buying things at the wrong time?
You did not buy the wrong thing. You bought the right thing on the wrong day. Put five purchases in below and see what that day may have cost you, with every study we used printed right next to it.
We see a red badge and feel like we just beat the system.
Here is the part almost nobody checks: whether we actually did.
Here is an embarrassing thing most of us do. We see “-40%” on a thing we already wanted, feel a little spark of genius, and buy it. I have done this. You have done this. The badge makes us feel like we beat the system. So a UK consumer group decided to check who actually beats whom. They tracked 175 Black Friday deals for a full year, every single day. 83% of those items cost the same or less on some random Tuesday nobody was excited about. Read that again: the special day was usually not the special day. The problem is simple once you see it: a sale is a date. A low price is a fact about the year. The calculator below shows what that gap might be costing you.
The timing calculator
Runs in your browser. Nothing is sent anywhere.Quick question: what did you buy this year, and when? Up to five things. No name, no email, no account, nothing leaves this page.
Buying on sale and buying cheaply are two different hobbies
Which? did the boring work so nobody else has to. They watched 175 products across eight big shops for a whole year, from May 2024 to May 2025, not just during the noisy bit in November. Of those 175 deals, 83% were the same price or cheaper at some point outside the four-week sale window.
The finding about the day itself is harsher. Not one of the deals they tracked hit its lowest price of the year on Black Friday. Not one.
So the discount was real, and the low price was somewhere else in the calendar. Before you take this too far: this is 175 products in the UK, not every product on earth. It is a strong hint about how sales work, not a law of physics.
Source: Which?, price analysis of 175 products across eight retailers, May 2024 to May 2025, published 25 November 2025. which.co.uk
The same study, retailer by retailer
Same study, split by shop. Each bar is the share of tracked products that cost the same or less outside the Black Friday window:
Which?, same study. For Amazon, 63% of the tracked products were not merely matched but actually cheaper at another point in the year. The research is British and the retailers are British, so read the pattern rather than the exact percentage if you shop elsewhere.
Why the number on the tag will not sit still
It helps to know that a price online is not a decision somebody made once and wrote on a card. Profitero counted Amazon changing prices more than 2.5 million times a day, as reported by Quartz. Walmart and Best Buy each made about 50,000 changes in the whole of November. That is a whole month for them against a single day for Amazon.
At the same scale you can barely see the other two bars. That is the point. In a shop that reprices millions of times a day, the number you saw was never the price of the product. It was the price of the minute you happened to look.
Source: Quartz, reporting Profitero data. qz.com
When to buy what
The grid below is a month-by-month buying guide from Navy Federal, sorted into the seven categories the calculator uses. Treat it as a pattern, not a price feed. It suggests when things tend to get cheaper. It has no idea what anything costs today, and the calculator only uses it for one job: telling a likely month from an unlikely one.
Source: Navy Federal Making Cents, month-by-month buying guide. navyfederal.org. Similar month-by-month roundups: Kiplinger, US News.
One purchase, worked all the way through
Let us do one properly, with nothing hidden. You bought a television for $600 in November, in Black Friday week. The calculator says $30 to $78. Where on earth does that come from?
- What it knows. November is one of the months the guide points at for televisions, so your timing was sensible. It also knows you bought during Black Friday week, and Which? found that a sale label is not proof of a low price.
- What it has no clue about. Whether this exact television was $560 in September or $700 in March. There is no price history in here, and there never will be on a page like this one.
- Why the sale makes the range wider, not narrower. A good month would normally start the range at zero. The sale label pushes the bottom up to 5%, because a discount tells you the price moved. It does not tell you the price landed at the year’s low.
- How to actually read it. $30 to $78 on a $600 television is the size of the question, not a bill you paid. The line worth reading is the status: bought in a named month, during a sale. Translation, your timing was probably fine and there was not much left on the table.
Now run the same television through as an ordinary June purchase. The status flips to outside the named months, the range moves to 7% to 18%, so $42 to $108, and the advice underneath changes with it. That is the entire machine. There is nothing else in the box.
None of this tells you whether you should have bought the thing.
Perfect timing on something you used twice is still money gone. This calculator answers one narrow question: what the date cost you. Whether the purchase made any sense is a much bigger question, and that one is yours.
Three moves that do almost all of the work
Next time you want something, save the product page instead of buying it. The wanting and the paying stop being the same moment, which is most of the battle.
Pick the number where you would buy without thinking twice. A number you wrote down before the sale survives the sale. A number you invent during it does not.
Choose when you will look again: next week, or the month the guides point at. Checking every day is just urgency wearing you down slowly.
Tell me the thing and the price that would make it an easy yes. If today is not that price, waiting is a real answer, not you being indecisive.
Four things you are probably about to ask
“I need it now though”
Then buy it now. Timing only helps when the thing can wait. A broken washing machine is not a timing decision, it is a Tuesday.
“What about weird one-off stuff?”
Buying guides describe things shops restock every year. A rare item, a second-hand item or the last one in your size does not live on that calendar. Ignore the estimate and buy it when you find it.
“What if the price goes up, or it sells out?”
Both happen, and waiting has a cost. We are not going to pretend otherwise. That is exactly why the advice is name your price and pick a date to check again, rather than wait forever and call it discipline.
“I buy this every month anyway”
Then the move is stocking up in a good month, not hunting for a good day. The estimate still works, but your saving comes from buying more at once.
Where we come into it
This is normally the paragraph where an article promises software that watches every price for you while you sleep. Ours does not do that by itself. In dEssence you save a product, and then you switch on price or stock watching for that item yourself. Saving something does not start watching it. We would rather tell you now than have you find out in three months. And when an alert does turn up, it is a nudge to go and look, not an instruction to buy.
You are not paying for the product. You are paying for the day you decided.
On any one purchase that gap is small. Across a year of them it stops being small.
How this calculator works, and what it cannot know
What it does not do. It does not look up the price history of your item. We have no price database, and dressing up a number to look like we do would be lying. Nothing you type leaves your browser.
What it does. For each purchase it asks one question. How far is that month from the months the published guides name for that category, and was there a sale label on it? Then it applies a percentage range to what you paid.
- Bought in a month the guide names for the category: 0% to 6%.
- Bought in the month either side of one of those: 3% to 11%.
- Bought well outside those months: 7% to 18%.
- Bought during a promotion: the range widens rather than narrows, to at least 3% to 9%, and to at least 5% to 13% in Black Friday or Cyber Monday week. A sale label does not protect the purchase. Among the 175 deals Which? tracked, 83% matched or beat the sale price at another point in the year, and none of them hit the year’s low on the day.
Where the ranges come from. The months come from the Navy Federal guide. The behaviour of sale pricing comes from Which?. The percentages are ours. We picked them, they are deliberately cautious rather than research findings, and we set them so the bottom of the range is often zero and the top stays below a normal seasonal discount.
The yearly figure just spreads what you typed across 12 months. It is not a forecast. Put in two purchases from one month and it cheerfully assumes twelve months exactly like that one.
Sources on this page: Which? Black Friday price tracking, Quartz on Amazon repricing (Profitero data), Navy Federal month-by-month guide.