Differential counter · Free · No sign-up
Differential Cell Counter
A differential cell counter tallies each class of white blood cell as it is identified down the microscope, then reports each as a percentage of the cells counted. This one has a key for each of the six routine classes, stops automatically at 100 or 200 cells, and shows the percentages as you go.
It replaces a handheld differential counter, which typically costs $100 to $400.
| Cell type | Count | Percent |
|---|
Six keys, a running total that stops itself at the target, and percentages calculated as you count, so nothing needs working out at the end of a hundred cells.
A differential cell counter is a tallying device with one key per cell class, used to record a manual white blood cell differential by classifying consecutively encountered leukocytes on a stained blood smear.
- No sign-up
- No ads
- Counts never leave your browser
- Works offline
- Unlimited counters
Key facts
| Detail | Answer |
|---|---|
| Price | Free. Handheld differential counters run about $100 to $400 |
| Cell classes | Six: neutrophil, band, lymphocyte, monocyte, eosinophil, basophil |
| Keys | N, B, L, M, E, S, or tap the buttons |
| Target | 100 or 200 cells, with an automatic stop |
| Percentages | Calculated live as you count |
| Undo | Yes, last 100 entries, or Ctrl+Z |
| Where counts are stored | This browser only, never a server |
| Works offline | Yes, once the page has loaded |
| Identifies cells | No. Classification is the operator's; this holds the tally |
How to run a manual differential
The count is relative, so what matters is that the hundred cells are consecutive and unselected.
Set your target
100 cells is the routine convention. Choose 200 where more precision is wanted.
Work the monolayer
Count in the area of the smear where cells are evenly spread and not overlapping, following a consistent pattern so no field is counted twice.
Press a key for each cell
N, B, L, M, E or S as you classify each consecutively encountered white cell. The buttons do the same if you would rather tap.
Correct a miskey with Undo
Undo or Ctrl+Z removes the last entry. Do not guess at a correction afterwards; the running total is what the percentages come from.
Stop at the target and copy out
Counting halts automatically at the target. Copy results puts the counts and percentages on your clipboard, ready to paste into a report.
Who uses a differential counter
Anywhere a stained smear is read by eye rather than by an analyser, or where an analyser's result needs confirming.
Haematology laboratories
Confirming an analyser flag, documenting a left shift, or reading a smear the analyser could not classify.
Veterinary practice
Species differences mean manual differentials remain routine in veterinary haematology, where analyser reference data is thinner.
Teaching and training
Students learning morphology count alongside a supervisor, comparing two independent hundreds on the same smear.
Research
Where the stricter 200-cell convention and two independent operators are the standard.
Field and low-resource settings
The page works offline once loaded, which matters where a handheld counter is not available and connectivity is not either.
Proficiency testing
Repeat counts on the same slide to check operator agreement.
How a manual differential works
A manual differential classifies 100 consecutively encountered white cells in the monolayer of a stained smear and reports each class as a percentage of that hundred. The count is relative, not absolute: it says what proportion of the white cells were lymphocytes, not how many lymphocytes are in a litre of blood.
Where more precision is wanted, the stricter convention is 200 cells, and for research work counted independently by two operators. The selector above switches the target between the two.
| Class | Key | What it covers |
|---|---|---|
| Neutrophil | N | Mature segmented neutrophils |
| Band | B | Immature neutrophils. Counted separately because a rise in bands is what a “left shift” means |
| Lymphocyte | L | Lymphocytes of any size, including reactive forms |
| Monocyte | M | Monocytes |
| Eosinophil | E | Eosinophils |
| Basophil | S | Basophils. Takes S because B is already the band key, which is also how the keys are lettered on several physical counters |
Why bands are counted separately
Bands are immature neutrophils, and the reason they get their own key rather than being folded into the neutrophil count is that the proportion of them is itself the finding. An increase in bands is what is meant by a left shift, and documenting a left shift is one of the main reasons a manual differential is performed at all when an analyser has already produced numbers.
What this tool does and does not do
It counts. It does not identify. Classification happens at the microscope, by the operator. This page holds the tally, stops at the target, and converts the counts to percentages so that arithmetic is not done by hand at the end of a hundred cells.
It carries no reference ranges and no interpretation, deliberately. Normal ranges vary by laboratory, by analyser, by patient age and by species, and a web page is the wrong place to assert them. Report against your own laboratory’s ranges.
Counts stay in this browser and are never sent anywhere, which also means they are not a record. Copy the results out when the count is finished.
Online counter vs a clicker, an app, paper and a spreadsheet
Every counting method trades something away. This is what each one actually costs you.
| Feature | This online counter | Handheld clicker | Counter phone app | Pen and paper | Spreadsheet |
|---|---|---|---|---|---|
| Cost | Free | $5–$15 | Free with ads, or paid | Cost of paper | Subscription |
| Anything to install | No | Buy the device | App store download | No | Yes, or a web login |
| Several counts at once | Unlimited | One per device | Usually limited | Yes, messy | Yes |
| Fix a miscount | Undo and redo | Start over | Sometimes | Cross it out | Edit the cell |
| Counts by more than one | Any step size | One at a time | Sometimes | Manual maths | Yes |
| Below zero | Yes | No | Rarely | Yes | Yes |
| Keeps the count if you close it | Saves automatically | Until you reset the dial | Yes | If you keep the paper | Yes |
| Works with no signal | Yes, after first load | Yes | Yes | Yes | Often not |
| Keyboard and shortcuts | Full | None | None | None | Partial |
| Sends your data anywhere | Never | Never | Often, for accounts and ads | Never | Yes, to the cloud |
Other counter types
The same counter, set up and explained for a specific job. Your counters are shared across all of them.
Online counter
The all-purpose counter. Any step size, any number of counters, negative values allowed.
Open online counter →Tally counter
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Open lap counter →Rep counter
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A scoreboard for cards, darts and board games. One counter per player, negatives allowed.
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Open tasbeeh counter →Multi counter
Run as many counters as you like at once, side by side in a grid.
Open multi counter →Pitch counter
Count pitches, then get the rest days owed and the next eligible date.
Open pitch counter →Auto counter
Counts on its own from every 0.1 seconds to once an hour, and stops at your limit.
Open auto counter →Click speed test
Measure your clicks per second over 1 to 60 seconds, with your personal best kept on-device.
Open click speed test →
Frequently asked questions
How many cells are counted in a manual differential?
One hundred consecutively encountered white cells is the routine convention, with each class reported as a percentage of that hundred. Where more precision is required the count is extended to 200 cells, and for research it is commonly performed independently by two operators on the same smear.
What cell types are counted in a WBC differential?
Six classes in a routine differential: neutrophils (mature segmented forms), bands (immature neutrophils), lymphocytes of any size including reactive forms, monocytes, eosinophils and basophils. Abnormal or unclassifiable cells are noted separately rather than forced into one of the six.
Why are bands counted separately from neutrophils?
Because the proportion of bands is itself the finding. Bands are immature neutrophils, and an increase in them is what is meant by a left shift. Documenting a left shift is one of the main reasons a manual differential is done when an analyser has already produced a result.
Is a manual differential a percentage or an absolute count?
A percentage. It reports what proportion of the counted white cells fell into each class, not how many cells are present per unit volume. An absolute count requires the total white cell count from an analyser or a haemocytometer, multiplied by the percentage.
Can this replace a handheld differential counter?
For the tallying, yes: it has a key per class, an automatic stop and live percentages, where a handheld unit costs roughly $100 to $400. A handheld has the advantage of tactile keys you can use without looking, which matters when your eyes stay at the eyepieces.
Does this tool identify cells for me?
No. Classification happens at the microscope and is the operator's. This page holds the tally, stops at the target and converts the counts to percentages. It carries no reference ranges and makes no interpretation.
Are my counts saved?
They persist in this browser between page loads, so a reload will not lose a count in progress. They are never sent to a server, which also means they are not a record. Copy the results out when the count is finished.
Can I count 200 cells instead of 100?
Yes. The target selector switches between 100 and 200, and the automatic stop follows it. Two hundred is the stricter convention where the extra precision is wanted.
Counting guides
Longer answers to the questions behind the counting.
- Swimming
How to count laps while swimming
Why swimmers lose count at length 14, and five methods that actually hold up.
- Tallying
Tally marks explained
Groups of five, the five-bar gate, and why the convention has survived for centuries.
- Events
How to do an accurate headcount
Counting people is easy. Counting them accurately, twice, is not.
- Habits
Track a daily habit streak
Why streak apps fail, and what a plain daily counter does better.
- Click speed
How to click faster
Hardware and grip account for most of the gap. Practice accounts for less than people think.
- Inventory
How to do a stock take
Counting is the easy part. Preparing, and knowing your count is right, is the job.
- Training
Reps and sets explained
How to read a programme, and why the rep range matters more than the total.
- Reference
Types of counters explained
Synchronous vs asynchronous, mod-N, ring and Johnson, plus mechanical and software counters.
- Build it
How to make a counter
Twenty lines gets you counting. Here is what to add after that, and why.
- Baseball
How to keep an official pitch count
Little League requires an official recorder at every game. Almost nobody explains the job.