Coverage calculator
Compare how many people you need against how many you have assigned to spot gaps and overstaffing.
Demand by slot
Summary
1 short for the day.
Plan with real coverage
Set requirements per role and slot; ShiftCal warns about gaps before you publish the roster.
A schedule can look perfectly staffed on paper and still collapse at half past twelve. That happens because most teams plan by daily headcount: five people on Tuesday, six on Saturday. A daily total says nothing about when those people are actually in the building. If everyone starts at ten and the rush hits at one, the day was "fully staffed" and the service still suffered. Daily headcount hides band-level gaps, and band-level gaps are where queues, complaints and overtime are born.
Coverage thinking replaces the daily total with a simple question asked slot by slot: how many people do we need between these two hours, and how many have we actually assigned? This calculator does exactly that. You define time bands, enter the required and assigned staff for each one, and it shows the difference per band — a gap, a surplus or an exact match — plus the overall balance for the day. The interesting insight is almost always in the bands, not in the total.
How do you estimate how many people you need per time band?
Start from the demand driver of your sector, not from habit. In hospitality it is reservations, covers or orders per hour; in retail it is footfall and transactions at the till; in healthcare and care work it is patient or resident ratios and care plans; in support and call centres it is contact volume and average handle time; in logistics it is deliveries, arrivals and dock slots. Whatever the driver, the method is the same: look at a few recent comparable days, note how the driver moves across the day, and translate it into people per band.
Then layer on constraints the raw numbers do not show: minimum safe staffing, roles that must always be present (a keyholder, a supervisor, someone certified), and known one-offs like a delivery, a promotion or a local event. The result is a required number per band that reflects reality instead of a flat average.
Why do both undercoverage and overcoverage cost money?
A gap is the visible cost: queues grow, service slows, sales walk out the door, quality and safety slip, and the people who are in take the strain. Gaps also generate the most expensive patch there is — last-minute overtime and frantic call-arounds.
A surplus is the invisible cost: you are paying wages for hours in which there is not enough work. It quietly raises your labour cost, and it often coexists with a gap elsewhere in the very same day — too many people in the quiet morning, too few at the peak. Undercoverage and overcoverage are the same planning error pointing in opposite directions, which is why a tool that shows both per band is more useful than one that only flags shortages.
How do you read the gaps — and what do you do about them?
In the calculator, each band gets a badge: a negative number means you are short, a positive number means you have more people than the band needs, and OK means required and assigned match. Read the pattern before touching anything: a surplus right next to a gap is the best news possible, because you can usually fix both with one move.
The classic fixes, in order of cost: move a shift — shift a start or end time so surplus hours slide into the gap; split a shift — turn one long flat shift into two shorter ones centred on the peaks; open a shift — publish the uncovered band so available part-timers or colleagues can claim it; and only then add hours or people. Also compare the band story with the totals: a balance of zero for the day can hide a gap and a surplus that cancel out.
Why should coverage review be a weekly loop?
Demand drifts: seasons change, a competitor opens, a menu or campaign changes the peak. Required numbers that were right in March can be wrong in June. Make coverage a short weekly ritual: after the week ends, compare what you planned with what actually happened — where you were slammed, where people stood around — and adjust the required numbers for the next week.
Two or three cycles of this loop are usually enough to converge on band requirements you trust. At that point the calculator stops being a diagnostic and becomes a template you tweak, and publishing a roster with confidence takes minutes instead of an evening.
A lunch peak that looks fine in the totals
- Define three bands: 10:00–12:00, 12:00–14:00 and 14:00–16:00.
- Enter what you need: 2 people for the quiet mid-morning, 4 for the lunch peak, 3 for the afternoon.
- Enter what the current roster assigns: 3, 3 and 3 — everyone on the same flat pattern.
- Read the bands: 10:00–12:00 shows +1 (one person over), 12:00–14:00 shows −1 (one person short at the busiest moment), 14:00–16:00 shows OK.
- Read the totals: 9 required, 9 assigned, balance 0 — the day looks perfect.
Result: The daily balance says everything is fine while the peak is understaffed and the quiet morning overstaffed. Move one start from 10:00 to 12:00 — or split one shift around the peak — and all three bands hit exact coverage with zero extra hours paid.
Frequently asked questions
How wide should a time band be?
One or two hours works for most teams. Use narrower bands around your peaks, where a single person more or less changes the outcome, and wider bands in flat parts of the day.
Is a surplus really a problem if my total hours match demand?
Yes. An idle hour at 10:00 does not serve the customer who walks in at 13:00. Totals that match while bands do not is precisely the failure mode this calculator exists to expose.
How do I know my required numbers are right?
You do not, at first — they are an estimate built from your demand driver and experience. Review them weekly against what actually happened and correct them. They converge quickly.
What if I cannot hire anyone to close a gap?
Most gaps are distribution problems, not headcount problems. Move start and end times, stagger shifts, split a long shift around the peak, or publish the band as an open shift for existing part-timers before assuming you need another hire.
Does the calculator store my data?
No. It runs entirely in your browser and nothing is saved or sent anywhere. If you want required-vs-assigned coverage per role with warnings before you publish the roster, that is what ShiftCal does — free for teams of up to 5 employees.