The calendar can look the same while the arithmetic is different
A compressed schedule keeps total weekly paid hours broadly unchanged but distributes them across fewer days. Reduced hours lower the weekly paid total. Both can remove a commuting day, but only the second necessarily buys back paid working time.
| Example | Weekly hours | Days | Average paid hours/day |
|---|---|---|---|
| Current pattern | 37.5 | 5 | 7.5 |
| Compressed 4-day pattern | 37.5 | 4 | 9.375 |
| Reduced 4-day pattern | 30 | 4 | 7.5 |
The compressed option removes one attendance day without reducing the 37.5 paid weekly hours. The reduced option returns 7.5 paid hours each week but may also reduce pay.
Annualise the difference
Using 46 working weeks, reducing from 37.5 to 30 hours returns 345 paid working hours across the year. If both options remove one commute costing £10 per day, each could also save about £460 in travel over those 46 weeks.
Paid hours returned/year = (current weekly hours − option weekly hours) × working weeksCommute saving/year = fewer working days/week × working weeks × commute cost/dayDo not ignore longer-day effects
Compressed days may change childcare windows, fatigue, meal costs, public transport availability or overtime opportunities even when salary is unchanged. Those effects are personal and cannot be inferred from weekly hours alone.
Worked pay comparison
Suppose the current arrangement pays £30,000 take-home for 37.5 hours over five days. A compressed four-day option keeps the same take-home pay and weekly hours, while a reduced-hours option pays £25,500 for 30 hours over four days. The compressed option preserves annual income but creates longer working days. The reduced option gives back 345 paid hours across 46 working weeks but reduces take-home pay by £4,500.
| Measure | Compressed | Reduced |
|---|---|---|
| Take-home change | £0 | −£4,500 |
| Paid hours returned/year | 0 | 345 |
| Commute days removed/year | 46 | 46 |
The same four-day calendar therefore represents two different exchanges. One trades shorter daily hours for longer days while preserving income; the other trades income for genuine working-time reduction.
Break treatment, holiday booking, pension implications and how a working day is defined can differ between employers. The calculator compares the figures you enter; it does not determine entitlement.