$56.98est. delivered
The lowest delivered 28S titled working, at $57. The title says READ, so check the description for the catch, and ask for a photo of the battery cover.
Vintage Hewlett Packard 28S Advanced Scientific Calculator - Works! **READ**
HP-28S
The HP-28C of 1987 was the first handheld to do symbolic algebra, and the HP-28S followed in January 1988 with sixteen times the memory, 32 KB, and directories to organize it. It folds open like a book. The left half has the letters, in alphabetical order, and the right half is a full RPN scientific keyboard. Inside it runs RPL, the language HP built on top of RPN, and it can solve and simplify equations as well as plot them. There's no way to connect it to a computer, only an infrared printer link. HP sold it until 1992 and replaced it with the HP 48 series, so it's the last of HP's pocket-sized RPL machines.
Good forCollecting
Spec at a glance
- Maker
- HP
- Type
- Graphing
- Launched
- 1988
- Made
- 1988–1992
- Entry
- RPN
- Display
- LCD
- Programmable
- Yes
- Memory
- 32 KB, with directories for variables and programs
- Language
- RPL, with symbolic algebra
- Display
- 137 x 32 pixel LCD, four lines
- Keyboard
- Flip-open clamshell: letters on the left, in alphabetical order
- Power
- Three N cells
- Also listed as
- HP 28S, HP28S
- Typical eBay ask (Oct 15, 2026)
- $80–$140
Bench check
Power, memory, display and keys
- Battery and power
- Three N cells under a sliding cover. The cover is the weak point: strong springs push on the cells, and the thin plastic notches the lid slides into crack, even on well-kept ones. Survivors often have tape or a rubber band holding the cover on.
- Memory
- 32 KB kept with the power off. There's no port to a computer, so nothing on it was ever backed up, and a dead set of batteries means starting from scratch.
- Display
- A four-line LCD: three stack lines and a menu line.
- Keys
- Two keyboards in a clamshell. The left half has the letters in alphabetical order, not QWERTY, and the right half is the scientific keyboard. Ask whether both halves work.
- Cards, ports and modules
- No card slots and no computer link, only an infrared output for HP's 82240 printer.
- Original, reissue or clone
- The HP-28C of 1987 looks the same but has only 2 KB and no directories. In hex mode, #A SYSEVAL shows Version 2BB on a 28S, and 1BB or 1CC on a 28C. The 18C and 19B share the clamshell body.
Should come with it
- The original battery cover in one piece
- The owner's manuals
Check the listing photos against this list, and ask the seller about anything you can’t see. A missing piece should come off the price.
What to check
The battery cover's notches crack, so check it's whole and stays on. A 28C sold as a 28S is the other trap.
- 01Battery cover: Ask for close photos of the battery cover and the plastic beside it. A whole cover that clicks on without tape is what you want.
- 02Version: Ask the seller to run #A SYSEVAL in hex mode. Version 2BB means a 28S.
- 03Both keyboards: Ask whether every key on both halves registers. No dead or doubled keys is what you want.
- 04Display: Ask for a photo with the display on. All four lines should be clear and even.
- 05Hinge: Look at the hinge in the photos. Both halves should open flat and line up.
New to old calculators? The condition checklist covers battery corrosion, displays, keys and card readers, and RPN in one hour gets you typing on an HP.
Buying guide
Which one to buy
§ Oct 15, 2026We'd buy the 28S titled working at $67 delivered, well under the $80-140 band most working ones ask, and the cheapest titled tested with new batteries asks $97. There are at least 31 for sale, and boxed sets with the manuals ask $150-370, the top one about 3.4 times the $108 median. The battery cover is the weak point, since strong springs crack its thin notches, so ask for close photos of the cover and walk away from one held on with tape. The 1987 HP-28C looks the same with only 2 KB, so check the face says 28S and ask whether every key on both halves registers.
- Listed now
- 31
- For parts
- 1
- Typical ask
- $80–$140
- Full range
- $27–$350
Cheapest 
Best value $66.52est. delivered
Titled works, at $67 delivered from a 99.7% seller, well under the band with no caveat in the title. Ask for close photos of the battery cover, since that's what cracks.
Vintage Hewlett Packard 28S Advanced Scientific Calculator - Works!
View on eBay ↗: Vintage Hewlett Packard 28S Advanced Scientific Calculator - Works!$66.52 est. delivered
Best for beginners $125.00delivered
Titled tested with new batteries and a case, at $125 delivered with free shipping from a 100% seller. It's mid-band for a 28S you can open and use the day it arrives.
HP-28S Scientific Calculator w/New Batteries and case TESTED!
Easiest to get working $96.92est. delivered
Titled tested with new batteries installed, at $97 delivered, so the three N cells are already sorted. Ask for a photo showing the battery cover sits on without tape.
HP-28S Advanced Scientific Calculator Tested - New Batteries Installed
Delivered prices include shipping as eBay quoted it to a US address on Oct 15, 2026. Many sellers charge by distance, so your total may differ. eBay shows yours before you pay.
Snapshot
For sale on eBay
8 of 31 listedChecked . Some may have sold.
Delivered prices include shipping as eBay quoted it to a US address on Oct 15, 2026. Many sellers charge by distance, so your total may differ. eBay shows yours before you pay.
- Used
- Cheapest
Vintage Hewlett Packard 28S Advanced Scientific Calculator - Works! **READ**
$56.98est. delivered
$49.99 + $6.99 shipping
Buy It Now$49.99
Offers accepted
This seller takes offers, and many sellers accept less than the asking price.
Fine if you might miss it? Send an offer first. Someone else can still buy it while you wait for a reply.
Want it for sure? Use Buy It Now.
Good buy
Titled works, with READ, so check the description for a catch.
Seller: jacobarboz-1
99.8% positive
- Used
- Best value
Vintage Hewlett Packard 28S Advanced Scientific Calculator - Works!
$66.52est. delivered
$59.00 + $7.52 shipping
Buy It Now$59.00
Good buy
Titled works. Photo shows it open with the display off.
Seller: okthehunt
99.7% positive
- Used
- Best for beginners
HP-28S Scientific Calculator w/New Batteries and case TESTED!
$125.00delivered
$125.00 · free shipping
Buy It Now$125.00
Good buy
Titled tested, with new batteries and a case.
Seller: mthoople
100% positive
- Used
- Easiest to get working
HP-28S Advanced Scientific Calculator Tested - New Batteries Installed
$96.92est. delivered
$91.20 + $5.72 shipping
Buy It Now$91.20
Good buy
Titled tested, with new batteries installed.
Seller: all720883
99% positive
For partsHewlitt Packard HP 28S Scientific Calculator Vintage 1986 / Untested AS IS
$57.39delivered
$57.39 · free shipping
Buy It Now$57.39
Our take
Untested and sold as is. The 1986 in the title predates the 28S.
Seller: tech_revived
99.9% positive
UsedVintage HP 28S Advanced Scientific Calculator - 1988 USA Made - Tested & Working
$108.27est. delivered
$100.00 + $8.27 shipping
Buy It Now$100.00
Our take
Titled tested and working, made in the USA in 1988.
Seller: findsaintjoseph
100% positive
UsedHewlett Packard HP 28S Calculator W/Box Manuals & Inserts(READ Description )
$150.00delivered
$150.00 · free shipping
Buy It Now$150.00
Our take
With box, manuals and inserts. The title says to read the description.
Seller: greenhornetbest
100% positive
Used- Check the seller
- Priced high
Hewlett Packard HP 28S Advanced Scientific Calculator Plus Manuals IN BOX
$370.00est. delivered
$350.00 + $20.00 shipping
Buy It Now$350.00
Priced high
Boxed with manuals, under the same title as another seller's set. About 3.4 times the median.
Seller: clrenn
100% positive
Prices change daily. The live eBay search shows everything listed now, including anything new since Oct 15, 2026.
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