How SalaryDex calculates your salary
Every figure on this site is derived from public datasets. This page explains exactly where each number comes from and how we combine them.
1. Salary data sources
Gross salary figures are taken from the ONS Annual Survey of Hours and Earnings (ASHE) 2025, which covers approximately 180,000 employee records across the UK. For each occupation we use the median, lower quartile (P25), and upper quartile (P75) annual gross earnings by Standard Occupational Classification (SOC) code.
Where city-level ASHE breakdowns are available we use them directly. For cities with insufficient sample sizes, we apply an ONS-published regional adjustment factor to the national median.
NHS salary figures are sourced separately — see section 5 below.
2. Tax calculation
Take-home pay is calculated using HMRC 2025/26 income tax bands and National Insurance thresholds. The personal allowance is £12,570. Income tax is applied at 20% (basic rate, £12,571–£50,270), 40% (higher rate, £50,271–£125,140), and 45% (additional rate, above £125,140). The personal allowance tapers to zero between £100,000 and £125,140.
National Insurance contributions are calculated at Class 1 employee rates: 8% on earnings between the Primary Threshold (£12,570) and the Upper Earnings Limit (£50,270), and 2% above £50,270.
Scottish income tax applies to residents of Edinburgh, Glasgow, and Aberdeen. Scotland has its own bands: starter rate 19% (£12,571–£14,876), Scottish basic rate 20% (£14,877–£26,561), intermediate rate 21% (£26,562–£43,662), higher rate 42% (£43,663–£75,000), advanced rate 45% (£75,001–£125,140), and top rate 48% above £125,140. National Insurance uses UK-wide thresholds regardless of Scottish residency.
Student loan repayments are not included by default, as repayment plans vary widely. Pension contributions are included only for NHS pages, where AfC pension rates apply.
3. Rent figures
Monthly rent is the Rightmove average asking rent for a one-bedroom flat, Q4 2025, covering the city's core postcode districts. We use one-bedroom figures as the baseline because they represent the minimum viable solo living cost — the most relevant benchmark for a single professional evaluating a job offer.
Rightmove asking rents tend to slightly lead achieved rents. Where ONS Private Rental Market Statistics (PRMS) data for the same period showed a meaningful divergence, we blended the two sources at a 60/40 Rightmove/PRMS weighting.
4. Cost of living
City cost-of-living indices are derived from Numbeo 2025 city data, indexed to London = 100. The composite index covers groceries, restaurants, local transport, utilities, and leisure — excluding rent, which is handled separately.
The Numbeo index is used to calculate purchasing power equivalence on the “equivalent salary” pages. A salary of £X in London is equivalent to £X × (target city COL ÷ 100) in the target city for the same basket of goods and services.
Cost-of-living data is inherently subjective and varies by personal spending pattern. Our indices should be treated as indicative rather than precise.
5. NHS salary calculation
NHS Agenda for Change (AfC) pay scales are sourced from NHS Employers 2025/26. Each band covers a range of pay points; we use the midpoint of the published scale unless a specific point is more commonly cited for entry-level roles (e.g. Band 5 point 2 for newly qualified nurses).
High Cost Area Supplements (HCAS) are added for London-area trusts. Inner London HCAS is 20% of basic pay (minimum £4,551, maximum £8,059). Outer London HCAS is 15% (minimum £4,218, maximum £5,437). Fringe HCAS is 5% (minimum £1,192, maximum £2,011). The appropriate zone is applied based on the city selected.
NHS pension contributions follow the AfC tiered employee contribution schedule for 2025/26 (ranging from 5.2% to 12.5% depending on pensionable pay), plus the 23.7% employer contribution rate. Both are shown separately on NHS pages.
Foundation Doctor (FY1/FY2) salaries use the 2025/26 national scale published by NHS Employers, with London HCAS applied where applicable.
6. Rent-to-income ratio
The rent-to-income ratio (RTI) expresses monthly rent as a percentage of monthly net take-home pay. It is calculated as:
The 33% threshold is a widely cited affordability benchmark: spending more than one-third of net income on rent is generally considered financially stretched for a single person. At 50% RTI, day-to-day discretionary spending becomes very constrained. Above 80% RTI, the salary is effectively unliveable in that city without a second income or shared accommodation.
RTI is calculated on net pay (after income tax and NI) rather than gross pay, which gives a more realistic picture of the actual financial pressure.