Track what your groceries cost over time
Krataa follows the things you buy again, from your own receipts. It shows whether each one cost more or less than usual, and it compares only the same kind and size. This part of the app is called the Shelf.
For iPhone, iOS 16.4 or later. In beta, on TestFlight by invitation.The waitlist opens at the foot of this page
Shelf
Ground coffee
$8.99new size
10 oz · Marlow Grocer · $0.90/oz
One more of this kind and size and its price line starts here.
Sample data: the coffee's own screen in Krataa, from the same 14 receipts as the year drawn below.
Ground coffee
12 oz bag13 receipts · $6.99 to $8.99
Oct 11, 2025 $7.49
Grnd coffee 12oz7.49
Grnd coffee 12oz7.49
Grnd coffee 12oz6.99
Reg 8.29 you saved 1.30
Sep 12 · $8.99
10 oz bag1 receipt · $8.99
Grnd coffee 10oz8.99
- Nov
- Jan 2026
- Mar
- May
- Jul
- Sep
The last 90 days. Usual is worked out from these receipts only.The bag changes size. The old line stops and a new one starts.
Grnd coffee 12oz7.49
1Oct 11, 2025
The first receipt is a dot. The coffee is on the Ledger. It is not on the Shelf yet.
Grnd coffee 12oz7.49
2Nov 8, 2025
The second makes a line. A thing joins the Shelf once it is on two receipts.
Grnd coffee 12oz6.99
Reg 8.29 you saved 1.30
3Apr 25, 2026
"Marlow Grocer printed: regular price $8.29, you saved $1.30." Krataa quotes a sale saving because the receipt printed it. It never works out a regular price.
Grnd coffee 10oz8.99
4Oct 10, 2026
A smaller bag starts again. The same $8.99, for 10 ounces. It reads new size, with no arrow.
The fourteen receipts behind this chart, as a table
Sample data. Ground coffee, every fourth Saturday at Marlow Grocer.
| Receipt | Day | Size | Price | Per ounce | Note |
|---|---|---|---|---|---|
| 1 | Oct 11, 2025 | 12 oz | $7.49 | $0.62/oz | |
| 2 | Nov 8, 2025 | 12 oz | $7.49 | $0.62/oz | Second receipt: it joins the Shelf |
| Second receipt: it joins the Shelf | |||||
| 3 | Dec 6, 2025 | 12 oz | $7.79 | $0.65/oz | |
| 4 | Jan 3, 2026 | 12 oz | $7.79 | $0.65/oz | |
| 5 | Jan 31, 2026 | 12 oz | $7.99 | $0.67/oz | |
| 6 | Feb 28, 2026 | 12 oz | $7.99 | $0.67/oz | |
| 7 | Mar 28, 2026 | 12 oz | $8.29 | $0.69/oz | |
| 8 | Apr 25, 2026 | 12 oz | $6.99 | $0.58/oz | On offer: the receipt printed a saving of $1.30 |
| On offer: the receipt printed a saving of $1.30 | |||||
| 9 | May 23, 2026 | 12 oz | $8.29 | $0.69/oz | |
| 10 | Jun 20, 2026 | 12 oz | $8.49 | $0.71/oz | |
| 11 | Jul 18, 2026 | 12 oz | $8.49 | $0.71/oz | |
| 12 | Aug 15, 2026 | 12 oz | $8.99 | $0.75/oz | |
| 13 | Sep 12, 2026 | 12 oz | $8.99 | $0.75/oz | |
| 14 | Oct 10, 2026 | 10 oz | $8.99 | $0.90/oz | New size: a new line starts, with no arrow |
| New size: a new line starts, with no arrow | |||||
Sample data. The two lanes, the band and the numbered slips are this page's drawing. In the app, an item's screen draws one price line, for the kind and size you bought last: the coffee's, at the top of this page, waits for a second 10 ounce bag.
How it worksThe middle price of your other receipts
What usual means, exactly.
Every row on the Shelf sets your latest price beside your usual one. Usual is the middle price of your other receipts in the last 90 days, for the same kind, brand and size.
How to keep a grocery price book, on paper or in a spreadsheetUnsalted butter
1Every receipt, by the day it was bought
The last 90 days, Jul 15 to Oct 13
- $4.19Jun 27Older. Left out
- $4.49Jul 25Counted
- $4.29Aug 8Counted
- $4.69Aug 22Counted
- $4.49Sep 5Counted
- $4.39Sep 26Counted
- $4.79Oct 10The latest
- $4.29
- $4.39
- $4.49The middle one
- $4.49
- $4.69
2The other five, in order of price. The middle one is the usual price.
Usual$4.49Latest, Oct 10$4.79Against usual+$0.30Last time it was $4.39. Krataa compares with the middle of the five, not with last time, so one cheap week or one dear one does not set the mark.
What Krataa checksA new size is never an arrow
Like with like, or no arrow.
An arrow on the Shelf means one thing: the same kind and brand, at the same size, cost more or less than usual. Things sold by weight are compared per pound.
A different size or kind gets a quiet note. It never gets an arrow.
Grnd coffee 12oz8.99
Sep 12 · 12 oz for $8.99$0.75/oz
Grnd coffee 10oz8.99
Oct 10 · 10 oz for $8.99$0.90/oz
The same $8.99 buys two ounces less.
The size is on the receipt, so Krataa sees it change. The smaller bag gets a note in place of an arrow, and the price per ounce is shown for both.
- Ground coffee10 oz · Marlow Grocer · $0.90/oz$8.99new size
A new size. A note, and no arrow.
- Large eggs12 ct · Marlow Grocer · 29¢ each$3.49$0.50
The same kind and size as before. An arrow.
Grnd coffee 12oz6.99
Reg 8.29 you saved 1.30
"Marlow Grocer printed: regular price $8.29, you saved $1.30."A sale saving is quoted only where the receipt printed one, and as the store printed it. Krataa never works out a regular price.
Ground coffee: the 12 oz is the better buy
$0.75/oz in the 12 oz, $0.90/oz in the 10 oz. Saves $1.80 on 12 oz.
CompareNot now
The gap between two sizes, kinds or stores is worked out.When one size, kind or store cost less per unit than another you bought in the last 90 days, a card on the Shelf says so, and by how much. Between two sizes the gap has to be at least 10% per unit and come to at least $0.50. This is the card these two bags get.
The ShelfA thing joins on its second receipt
One figure for your latest buys, and where it comes from.
The top of the Shelf adds up what your latest buys cost against usual, and lists them under Went up, Went down and Steady. Only a like for like move counts.
It is a sum of what moved. It is not an inflation rate, and not a saving.
What you buy and what it costs now
Where the +$0.67 comes from
- +$0.50Large eggs$0.50 more than usual
- +$0.30Unsalted butter$0.30 more than usual
- −$0.13Bananas$0.06/lb less, on 2.14 lb
- $0.00Whole milkSteady. Nothing to add
- $0.00Ground coffeeNew size. Nothing to compare with
- +$0.67Latest buys vs usual$0.80 up, less $0.13 down
The Shelf screen, drawn with sample data: the five things on the receipt at the top of the home page.
DiscoverNo price published yet
Discover, for what other households paid, starts empty.
Everything above comes from your own receipts. Prices from other households are a separate part of the app, and today there are none to show.
Discover is the part of Krataa that compares your prices with what other households paid. It is built, and it is empty: no price has been published yet, because a price needs 5 households and the beta is small.
5 households, one price. A price shows only when at least 5 households bought the same thing at the same store chain, in the same state, in the same week.
The middle price, rounded to 5 cents. Before any coupon, updated every Monday, covering the last 12 weeks.
Store chains only. Discover compares a list of store chains in the United States. A local shop is on your Shelf like any other store, and is not in Discover.
Only with a yes from everyone. A household's prices count only while every member has said yes, and never say who paid.
Not yetWhat is not built is printed in red
What it does not do yet.
Where the Shelf cannot compare like with like, it says why in two or three words and draws no arrow. These four rows wear four of the notes it uses.
- Ground coffee10 oz · Marlow Grocer · $0.90/oz$8.99new size
new sizeA size you have not bought before. It starts its own line.
- CarrotsOrganic · Marlow Grocer$1.75/lbnew kind
new kindA different kind or brand of something you buy.
- CheddarTern & Tide Market$5.49size not printed
size not printedThe receipt printed no size or weight, so there is nothing to compare by.
- Dish soapMarlow Grocer$3.79details coming
details comingAn older line whose kind and size are still being filled in.
Krataa
The Shelf
What it does not do yet
Merge or split itemsNo
Per pound, no weightCannot compare
Usual past 90 daysNot counted
A regular price worked outNever
Stores not shoppedNo prices
Other householdsNone yet
An inflation rateNo
In beta
QuestionsEach answer starts with the answer
Common questions.
Is there an app that tracks grocery prices?
Krataa tracks what you paid, from your own receipts. It is an iPhone app, in beta. It does not show today's shelf prices at stores, and it does not follow national price trends.
Can I see the price history of something I buy?
Yes, for anything you have bought on two or more receipts. Its screen draws its price over time as a line, one kind and size at a time.
What does usual mean?
Usual is the middle price of your other receipts in the last 90 days, for the same kind, brand and size. The receipt being compared is left out, and so is anything older than 90 days.
How many times must I buy something before it shows up?
Twice. A thing joins the Shelf once it is on two or more receipts. A thing bought once stays on its receipt in the Ledger.
What happens when a package changes size?
The new size starts its own line and gets a note, never an arrow. The price per ounce, per pound or per item is shown for each size, so you can see the difference yourself.
Does it compare prices between stores?
Between the stores you have shopped, yes. An item's screen sets every kind, size and store you bought side by side, priced per unit. What other households paid comes through Discover, which starts empty.
Does it tell me how much I saved?
Only in two cases. A sale saving is quoted only as the receipt printed it, and Krataa never works out a regular price. And when one size, kind or store cost less per unit than another you bought, a card on the Shelf names the better buy and says by how much.
Is it only for groceries?
No. Anything you buy on two or more receipts joins the Shelf. Things sold by weight or pumped by the gallon are compared per pound or per gallon.
Does it work out my own inflation rate?
No. It adds up what your latest buys cost against usual, and lists what went up, what went down and what held steady. It gives no percentage for the household.
Do I have to type prices in?
No. The prices come from the receipts you add, once automatic itemizing is turned on. With it off, receipts are saved and not itemized, so the Shelf has nothing to compare.
From the blogGuides that work with a notebook or a spreadsheet too
Longer reads.
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The idea behind the app6 min read
- Budgeting without linking your bank: five ways compared
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