Guaranteed hours calculator: average a worker's hours over a 12-week reference period

Guaranteed hours are the change zero-hours employers ask about most, and the one with the fewest settled numbers. This page does two things: it sets out exactly what is confirmed as of 3 November 2026, and it gives you a calculator to see what a 12-week offer could look like for the people on your rota today. Everything runs in your browser; nothing is sent or saved.

What's confirmed, and what isn't (3 November 2026)

If anything in this table changes, the dated rows are where it will show. Check the GOV.UK consultation page for the outcome before you act on any number here.

The calculator: average 12 weeks of hours

Enter the hours actually worked in each of the last 12 weeks (leave a week blank or put 0 if they didn't work). It's filled in with the government's own example from the consultation: 8 hours a week for 7 weeks, then 20 hours a week for 5 weeks.

How the 12-week reference period works

The Act says a guaranteed hours offer must require work for a number of hours that "reflects the reference period hours". In plain terms, the employer looks back over a set period, works out the hours the person regularly did, and offers a contract for that.

Here's how it fits together, as set out in the Act and the consultation:

1. The first (initial) reference period starts when the rules come into force for people already working for you, or on the first day of work for anyone who starts later. The government's preference is that it lasts 12 weeks.
2. At the end of each period, you work out whether each zero-hours or low-hours worker qualifies. As consulted on, they must have worked during the period, met the regularity test, and (for low-hours workers) worked more than their contracted hours. Exclusions and exemptions may be added by regulations.
3. You make the offer. It must reflect the hours they worked in the period. The Act also lets regulations require the days and times offered to reflect when they actually worked.
4. They accept or reject it. Under the Act, an offer that isn't answered in time is treated as rejected. Workers who reject an offer can stay on their current arrangement.
5. Later reference periods follow. Someone who turned down an offer, or didn't qualify the first time, may qualify after a later period. The consultation says later periods can't be used to reduce hours already guaranteed in a contract.

Mean or median: why it matters

The consultation's own example shows how much the choice of method changes the offer. A worker does 8 hours a week for 7 weeks, then 20 hours a week for 5 weeks:

For a hospitality team with a quiet January and a packed December, that gap can be large. Run your seasonal staff through the calculator above and you'll see which people it matters for.

Shift notice and cancellation pay

Guaranteed hours are one of three linked rights for zero-hours and low-hours workers. The other two, also not in force and also waiting on regulations, are:

• Reasonable notice of shifts. GOV.UK's factsheet says the government will use regulations to state how much notice should be presumed reasonable. It applies to changes the employer makes, so two staff agreeing a swap between themselves isn't a breach.
• Payment for shifts cancelled, cut short or moved at short notice. The amount and what counts as "short notice" will be set in regulations. No payment is due if the worker cancels, doesn't turn up, or voluntarily swaps a shift with a colleague.

Both rights also extend to agency workers. Our guide to rota notice and shift changes covers what you can do now to publish earlier and change less.

What to do with your rota now

You can't follow rules that haven't been written, but you can make the change painless when they arrive.

• Keep weekly hours for every zero-hours and low-hours worker. Whatever the final method, the offer is built from weekly hours actually worked. If you can't produce 12 clean weeks today, start now.
• Run the calculator for your regulars. Anyone who works steady hours most weeks is the person most likely to qualify for an offer. Talk to them early: some will want fixed hours, some won't.
• Look at your seasonal pattern. If December inflates everyone's average, plan how you'll staff the busy weeks.
• Publish rotas earlier and change them less. Reasonable notice and cancellation pay will reward venues that plan ahead.
• Keep a record of who changed a shift. A worker-initiated swap won't trigger a payment; a manager cancellation will.

For the bigger picture on contracts, holiday and sick pay, read our guide to zero hours contracts in hospitality and the Employment Rights Act for hospitality.

Where ShiftComplete helps

Guaranteed hours turn the rota into a record that matters. In ShiftComplete, casual staff set their availability on their phone weeks ahead, you add the events that change demand, and it builds a draft rota in seconds that's fair across the team. Labour cost shows while you build, so you staff to budget instead of sending people home early.

If you switch on clocking in and out, staff clock in and out on their phone or the shared tablet, you see hours worked against the rota, and you can download hours as a spreadsheet with a total per person: the weekly figures this calculator needs. Shift swaps (a setting you switch on) go from one named colleague to another and then to a manager or deputy for approval, so you can see who asked for each change.

£1.49 per staff member per month, every feature included, free for 60 days with no card needed.

This page is general information based on the Act and the government's consultation, not legal advice. The rules will be set in regulations that haven't been published yet: check GOV.UK, and speak to Acas or an employment adviser about a specific case.