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 keys for the six routine classes and Other, counts nucleated red cells beside the total, stops 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 |
|---|
Enter the analyser’s white count to correct it for the nucleated red cells counted.
Eight keys, as on a bench counter, 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
- Free to use
- 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, plus Other |
| Keys | N, B, L, M, E, S, O and R, or tap the buttons |
| Nucleated red cells | Counted beside the total, per 100 WBC, with the corrected white count |
| 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, S or O as you classify each consecutively encountered white cell, and R for a nucleated red cell, which is not added to the total. 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 (a “manual diff” in laboratory shorthand) 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 |
| Other | O | Any other white cell you would report separately: blasts, promyelocytes, myelocytes, metamyelocytes, plasma cells. Counted in the 100; note what they were |
| Nucleated red cell | R | Counted beside the white cells, not in the 100, and reported per 100 WBC (see nucleated red cells below) |
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.
Nucleated red cells, the Other key and the corrected white count
Bench differential counters are sold with eight or twelve keys, not six, and they are most of what a search for a differential counter returns. The keys beyond the six routine classes are for the cells a routine count leaves out, and the dearer models add a white count corrected for nucleated red cells. This page has the same two extra keys, and the correction:
| 8-key digital counter | 12-key counter (DIFFCOUNT) | This page | |
|---|---|---|---|
| Price | About $275 to $333 | About $1,083 | Free |
| Keys | 8 | 12, named on screen | 8: the six classes, Other and nRBC |
| Percentages | Calculated | Calculated, with totals by group | Live as you count |
| White count corrected for nRBCs | Not in the listings | Yes | Yes, from the count you type |
| Counts kept | The current count | 12 differentials | The current count, in this browser |
| Keys you can feel without looking up | Yes | Yes | No; a keyboard is the nearest thing |
Counting nucleated red cells
A nucleated red cell is not a white cell, so it is not one of the 100. Press R each time you meet one while counting the hundred: it is tallied beside the white cells, does not move the total toward the target, and is reported as nRBCs per 100 WBC. With a 200-cell target the figure is halved, so it is always per 100.
The reason to count them is the white count. An analyser that does not separate nucleated red cells counts them with the white cells, so its white count is too high by their share. The correction takes them back out:
Corrected WBC = WBC × 100 ÷ (100 + nRBCs per 100 WBC)
Type the analyser’s white count in the box under the results table, in whatever unit it reports, and the page does the sum with the nRBCs you counted. A whole count per microlitre comes back as a whole number; a count in × 109/L keeps two decimal places.
| White count | nRBCs per 100 WBC | Sum | Corrected |
|---|---|---|---|
| 12000 per µL | 5 | 12,000 × 100 ÷ 105 | 11,429 |
| 15.0 × 109/L | 20 | 15.0 × 100 ÷ 120 | 12.50 |
| 8.4 × 109/L | 3 | 8.4 × 100 ÷ 103 | 8.16 |
Some current analysers count nucleated red cells themselves and report a white count that is already corrected, as the 12-key counter above can; check which yours reports before correcting it a second time. When to correct, and from how many nRBCs, is set by each laboratory’s procedure, not by this page. The formula is the one taught in laboratory courses, for example in the Nova Scotia Community College haematology lab manual’s section on WBC correction for the presence of NRBCs.
The Other key
The six routine classes do not cover every white cell on an abnormal smear. Blasts, the immature granulocytes (promyelocytes, myelocytes and metamyelocytes) and plasma cells are white cells, so they belong in the 100, but none of the six keys fits them. Press O for them: they count toward the total and get a percentage like any class. One key cannot say what they were, so write down which cells made up the Other count, and if one kind matters on its own, keep a separate tally of it on the multi counter.
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 counts 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.
Work & field4
Counting that produces a record someone else relies on: stock, occupancy, lab work.
People counter
In and out at a door, with live occupancy against a capacity and a fix for drift.
Open people counter →Bird counter
A row per species recording the high count, so a circling flock is not counted twice.
Open bird counter →Inventory counter
A count sheet holding the book quantity beside the counted one, with the variance per line.
Open inventory counter →Knitting counter
Rows, pattern repeats and a shaping schedule that names the increase rows and then ends.
Open knitting counter →
All 72 counters, by category: Everyday (7) · Sport & scores (44) · Fitness & health (7) · Work & field (5) · Faith (9)
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; here they go on the Other key.
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.
How do you count nucleated red blood cells in a differential?
Count them beside the white cells, not among them. Press R each time a nucleated red cell appears while you count the 100 white cells; it does not move the total toward the target. The page reports them as nRBCs per 100 WBC, halving the figure for a 200-cell count, which is the number the white count correction uses.
How do you correct the white count for nucleated red cells?
Multiply the analyser’s white count by 100 and divide by 100 plus the nRBCs per 100 WBC. A count of 12,000 per microlitre with 5 nRBCs per 100 WBC becomes 12,000 × 100 ÷ 105, about 11,429. Type the analyser count under the results table and the page does the sum; check first that the analyser has not corrected it already.
Counting guides
Longer answers to the questions behind the counting.
- Reference
Types of counters explained
Synchronous vs asynchronous, mod-N, ring and Johnson, industrial and PLC counters, plus mechanical and software counters.
- Haematology
How to do a manual differential count
Why the pattern matters, how many cells is enough, and the imprecision built into the method itself.
- Inventory
How to do a stock take
Counting is the easy part. Preparing, and knowing your count is right, is the job.
- Birding
How to count a flock of birds
Blocks, tens, and why the number to report is the most seen at one time.
- Knitting
How to read knitting shaping instructions
Every 4th row, alt rows, at each end, AT THE SAME TIME — translated, with the rows they land on.