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Census in, nurses required out
A nurse-to-patient ratio is the number of patients one nurse is responsible for on a unit. The calculation is census divided by the ratio, rounded up: you cannot roster four-fifths of a nurse. This calculator does that per shift across a full day, and shows you the shortfall against the staff you actually have.
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How do I calculate nurse staffing ratios?
Nurses required is census divided by the ratio, rounded up. Enter the census per shift and the ratio your unit works to, and this does it, along with the gap against the nurses you have.
The ratio your unit is held to, by law, policy or contract.
| Shift | Census | Nurses on hand | Required | Over / under |
|---|---|---|---|---|
| Day | 5(4.4 ↑) | Short 1 | ||
| Evening | 5(4.4 ↑) | Short 1 | ||
| Night | 4 | Short 1 |
Required is census ÷ ratio, rounded up. The figure in brackets is the exact division, shown so the rounding is visible rather than silent; it is the step that gets skipped.
Nurses required
14
Across all three shifts, at the ratio above.
Day, Evening, Night: 3 nurses below the ratio you entered.
Computed in your browser. Nothing you type here is sent anywhere.
At a glance
- Nurses required is census divided by the patients-per-nurse ratio, rounded up. Twenty-two patients at 1:5 needs five nurses, not 4.4.
- Rounding up is the whole calculation. The fractional nurse is the one who does not exist, and averaging her away is how a unit is correctly staffed on paper and short on the floor.
- A ratio applies to a shift, not to a day. This calculator runs days, evenings and nights separately, because a unit can be staffed at 08:00 and two short at 23:00.
- California sets a 1:5 ratio on medical-surgical units under Title 22. Most states set none, and where there is no law the ratio is your policy; the calculator applies whatever figure you give it.
- It computes in your browser. Nothing is sent anywhere and there is no account.
How many nurses do I need for this census?
Divide the census by the patients-per-nurse ratio and round up. Twenty-two patients at one nurse to five is 4.4, which means five nurses, because 4.4 nurses is not a thing that can turn up.
The rounding is not a detail and it is the step that gets skipped. A unit that reports 4.4 required and rosters four has not made a small error; it has made the specific error of counting a nurse who does not exist, and it has done so in a way that looks arithmetically defensible on a spreadsheet. Round up, every time, per shift.
The second thing that gets skipped is that this is a per-shift calculation, not a per-day one. A day with plenty of nurses on it can be comfortable at eight in the morning and two short at eleven at night, and one number per day averages that into a figure that describes no actual moment of the actual day. The calculator above runs each shift separately for that reason.
And a caution about what the number means. This is a floor, not a plan. It assumes every patient is the same amount of work, which is false in a way everyone on a unit knows viscerally: a ratio is a headcount and headcounts do not know how sick anybody is. It also has nothing to say about admissions, discharges, transfers or the two hours somebody spends in a room they did not expect to be in. The number is the minimum below which you should not go, not the number at which the shift will be pleasant.
What is the required nurse-to-patient ratio?
It depends entirely on where you are, and for most of the United States the answer is that no law sets one; the ratio your unit is held to is your employer's policy or your contract.
California is the exception that everyone cites, and it is worth being precise about rather than gesturing at. Under Title 22 of the California Code of Regulations, licensed nurse-to-patient ratios are set in regulation, and medical-surgical units are held to one licensed nurse to five patients. That is a legal minimum at all times, not an average across a shift, and not something a busy hour excuses.
Beyond that specific claim this page will not tell you what your unit is held to, and you should be suspicious of any free calculator that does. Ratio law is state by state, unit by unit and shift by shift; it changes; and a page that hands you a confident table of numbers it cannot cite is a page that will eventually hand somebody a wrong one about a hospital they work in. Your state board of nursing and your employer's own policy are the sources that actually bind you. The calculator applies whatever ratio you give it, which is the honest shape for a tool that does not know where you are standing.
What the number cannot tell you
Whether the nurses it counted are the right nurses, whether they are allowed to be there, and whether the patients are as similar as the arithmetic assumed.
The calculation counts bodies with the right letters after their name. It does not know that one of them is on their fourth consecutive twelve, that another's certification lapsed on Friday, that a third is competent on this unit but not on the two beds that were just transferred in, or that the census of twenty-two includes a patient who is, by himself, most of somebody's shift. Every one of those turns a compliant number into an uncomfortable night, and none of them are visible from here.
Acuity is the largest of those gaps and it has its own calculator, linked below. The rest is the difference between a sum and a roster: MedAligna computes required staffing from the census you already entered, weights it by acuity, and turns the coverage row red the day a shift falls short: the same day, rather than at the end of the month when the period is closed and nobody can do anything about it.
Questions people actually ask
- How do I calculate the number of nurses needed?
- Divide the census by the patients-per-nurse ratio and round up, per shift. Twenty-two patients at 1:5 is 4.4, which is five nurses. Rounding down counts a nurse who does not exist.
- Why round up rather than to the nearest whole number?
- Because there is no such thing as four-tenths of a nurse, and the rounding direction is the entire safety margin. Rounding 4.4 to four is not a rounding error, it is a decision to run the unit above its ratio, made silently by a spreadsheet.
- Which states have mandated nurse-to-patient ratios?
- California sets ratios in regulation under Title 22: medical-surgical units at one licensed nurse to five patients. Other states have taken various approaches, from committee-based staffing plans to nothing at all, and it changes. We are not going to publish a table of state ratios we cannot cite to a primary source: check your state board of nursing, and check your employer's policy, because where there is no law the policy is the thing that binds you.
- Is the ratio an average across the shift or a minimum at all times?
- Under California's Title 22, it is a minimum at all times rather than a shift average, which is the distinction that matters most in practice, because it means the ratio is not satisfied by having been fine for most of the evening. Elsewhere, it depends on what your policy says, and it is worth reading it rather than assuming.
- Does this account for how sick the patients are?
- No. It is a headcount ratio, and a headcount ratio treats every patient as the same amount of work, which is false, and everybody on a unit knows it is false. That is what the acuity-based staffing calculator is for; it is linked at the foot of this page.
Sources
- California Code of Regulations, Title 22 — Licensed nurse-to-patient ratios – California Department of Public Health. Checked 2026-07-13.
Ratio and duty-hour requirements change, and they differ by state, by unit and by shift. These are the primary sources; your state board of nursing and your own employer's policy are what actually bind you.
Related
The coverage row that turns red the same day
MedAligna computes required staffing from the census you already entered, weights it by acuity, and flags the shortfall while you can still fix it. Fourteen days free.