How every number is worked out.
A decision tool you can't check is just a guess with a confident voice. So here's the whole working — the same sums the calculator runs in your browser, in plain English, each ending in a number from the built-in example (£52,000 vs £62,000) you can check for yourself.
You don't need to read this to use the calculator. It's here so you can look under the bonnet if you want to — skip it freely, or dip into the part you're curious about.
1 · What a job really costs your time
A job costs you more than its contracted hours — it costs you the travel it forces on you, too. Time you can actually use on the way in (reading or dozing on a train) counts for less; time you can't (driving) counts in full. A night away on business adds about an evening on top of the working day.
We turn your holiday into whole weeks off and work the same way for both jobs, so the comparison always stays fair.
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Hybrid uses the office-days figure you set; on-site counts five days a week, remote none. The five-days-a-week conversion for leave is a deliberate simplification — it stays fair because both jobs share it.
See it live: tap committed hours in the calculator and this unfolds with your own numbers.
2 · Your real take-home
"Gross" salary is a headline, not a wage. What lands in your account is what's left after income tax, National Insurance, your pension and any student loan. We work all of that out for the year, for England, Wales & NI or for Scotland.
One thing trips people up: how much tax your pension escapes depends on the way it's collected. The three common ways differ, so it's worth a glance — not sure which you're on? Your payslip or pension provider will say.
| The contribution escapes… | Salary sacrifice | Net pay | Relief at source |
|---|---|---|---|
| Income tax | ✓ | ✓ | ✓20% added in pot; higher-rate via tax return* |
| National Insurance | ✓ | ✗ | ✗ |
| Student loans | ✓ | ✗ | ✗ |
* The higher-rate reclaim arrives through a tax return, so it counts in your net position (section 3) but never in monthly take-home.
Current — £52,000 + £2,000 bonus
salary sacrifice · 5% pension · Plan 2
Offer — £62,000 + £5,000 bonus
net pay · 4% pension · Plan 2
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Income tax uses the selected year's bands, including the personal-allowance taper — above £100,000 you slowly lose your tax-free allowance, which the calculator handles for you. Employee NI is 8% between £12,570 and £50,270 and 2% above, worked out across the year. Student loans repay 9% (Plans 1, 2, 4, 5) or 6% (postgraduate) above each plan's own threshold, and plans stack. Benefits you mark as taxed — like private medical — are added on as benefits-in-kind.
See it live: every payslip row in the calculator unfolds its own band-by-band working on tap.
Self-employed (sole trader)
Set a role to self-employed and the engine taxes trading profit — income minus allowable expenses, the same two numbers as your Self Assessment — through the same income-tax bands (both nations). National Insurance becomes Class 4 (6% on profits between £12,570 and £50,270, 2% above); Class 2 is shown as an explicit £0 — it hasn't been mandatory since April 2024, and profits above the small-profits threshold still earn your State Pension year. Student loans apply the same thresholds to profit, collected through Self Assessment. Personal pensions get relief at source — you pay in from taxed income, your provider claims basic-rate relief into the pot, and higher-rate relief returns as the reclaim line — with no employer match. Leave is unpaid: committed hours use 52 weeks minus your weeks off, with no automatic bank holidays. And because freelance income honestly varies more than salary, the 20 what-ifs nudge a self-employed offer's profit by ±10% rather than ±£2,000 — so the steadiness verdict is harder to earn.
3 · The real difference per year
Take-home isn't quite the full picture either. A fair comparison adds what the job quietly gives you — employer pension and benefits — and takes off what it quietly costs you, like getting to the office. That's your real difference per year: the whole financial result of the move, not just the salary gap.
From the same sums we also work out your break-even salary — the offer salary at which you'd be no better or worse off than today. It's the single most useful number to walk into a pay conversation with.
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Employer pension is deferred pay, but real pay — so it counts in the yearly result. Cash-per-hour deliberately leaves it out, because you can't pay rent with it this month. ("Net position" is the technical name for the real difference per year.)
Family & childcare (optional)
Turn on the optional "Family & childcare" inputs and two high-earner traps join the real-difference figure, both keyed off your adjusted net income (income minus your gross pension contributions). The High Income Child Benefit Charge claws back 1% of Child Benefit for every £200 of adjusted income over £60,000 — all of it by £80,000. The £100,000 childcare cliff is harsher: at £100,000 of adjusted income, England's funded hours and Tax-Free Childcare are lost in full, in one step — so a pay rise can leave a family thousands worse off. Because pension contributions lower adjusted income, the tool shows when paying a little more in keeps the lot. We price the cliffs exactly; the £ value of the childcare you'd lose is yours to enter (it varies by region, hours and provider). Funded hours are England-only and the cliff is per parent.
4 · The life side — when money isn't the whole story
Pay is only half of a job, so we score five other sides of it from −5 to +5, where a plus means the new job is better: your time, wellbeing, growth, security and flexibility.
Two of those — time and flexibility — come straight from facts, so they count in full. The other three rest on how a job feels, and you can only really guess at a job you haven't started. So until you know a place well, those three are deliberately turned down: an impression from one interview counts for less than what an insider knows. That's why the life score moves cautiously and leans hardest on the things you can actually measure.
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Wellbeing blends stress, enjoyment, evenings and on-call; growth blends skills and promotion path; security is your stability rating. The final life score is the average of the five, weighted by your priority sliders. Because the "feel" scores are turned down until you know a job well, a big first impression makes a smaller dent than a hard fact like the commute — by design.
See it live: tap any life row in the calculator for this working with your own ratings.
5 · Turning it into one verdict
To reach a single answer, money and life go on the same −5 to +5 scale. Money gets there through your exchange rate — what a genuinely meaningful pay riseA figure you set: the yearly rise that would actually change something for you. It's how we turn pounds into points — so the same £3,000 means more to someone it would change than to someone it wouldn't. is worth to you — so the same £3,000 means more to someone it would change than to someone it wouldn't.
Then we blend the two using how much you said each matters. Your money priority is weighed against the average of your five life priorities, so the life side can't quietly count five times over. Both scores stay on screen the whole time — nothing is hidden behind the needle.
The sign points the way — minus means stay, plus means switch — and the band is how loud the call is. The same cut-offs apply on both sides of zero:
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A steadiness check then re-runs the verdict 20 times with small changes — pay ±£2,000, commute ±15 minutes, your priorities ±2, and so on. If any of them flips the answer, the verdict says so out loud rather than pretending to be sure.
6 · The five-year view
A pay rise compounds, and so does a pension. The chart line is the running total of choosing the offer: the spendable-cash difference each year, plus the growing gap between the two pension pots as they build and grow.
We hold tax rates at the selected year's — five years of Budgets can't be predicted honestly, so we don't pretend to.
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7 · What we deliberately don't model
An honest tool is clear about its edges. These are left out on purpose — named here so no gap is a surprise:
- Tapered pension annual allowance — only bites above roughly £260,000 of income.
- Auto-enrolment qualifying-earnings bands — we apply your pension % to your full salary; check your scheme.
- Minimum-wage floor on salary sacrifice — your payroll team enforces this, not a calculator.
- Pay-period-by-pay-period NI — we work it out for the year; uneven monthly pay can differ slightly.
- Limited companies — salary + dividends + corporation tax, and IR35/umbrella contracting; on the roadmap. Sole traders are modelled (see section 2) — payment-on-account timing and VAT aren't, since they don't change the yearly position being compared.
- Cost of living between places — rent in London versus elsewhere is a postcode-sized question only you can answer.
Rates come from official publications, carried for 2025/26 and 2026/27, last checked June 2026 and re-checked every April:
This is decision support, not financial or tax advice.