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Calculators Eleven instruments, every assumption stated

Run your own numbers

Simple tools for running your own numbers. Every assumption is stated on the page, results update as you type, and nothing you enter leaves your browser. They illustrate how the maths works — they don't tell you what to do.

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Tax year modelled
2025/26
Calculator Fees & costs § 01
  1. 01 Fee impact Compare two annual charge levels on the same pot and see what the difference compounds into over decades. Methodpot × (1 + (g − c) ⁄ 12)ⁿ, monthly, for each charge c Worked example £20k + £250/mo · 5% · 0.4% vs 1.5% · 25y −£38,900
  2. 02 Inflation impact What your money will really buy in 10, 20 or 30 years — and the return cash needs just to stand still. Methodreal value = £ ÷ (1 + i)ⁿ Worked example £10,000 · 3% · 20y £5,537 today’s money
  3. 03 Capital gains tax The £3,000 exemption, how gains stack on your income, and the 18%/24% split — with every assumption editable. Methodtax = Σ (gain − AEA) in band × rate Worked example £20,000 gain · £45k income £3,840 CGT
Calculator Saving & investing § 02
  1. 04 Compound growth What regular saving could grow into over time, and how much of the final pot is growth rather than your own contributions. MethodFV = P(1+r)ⁿ + c · ((1+r)ⁿ − 1) ⁄ r Worked example £250/mo · 25y · 5% £148,877
  2. 05 Emergency fund Set a cash buffer target from your monthly essentials and see how long it’ll take to build at your saving rate. Methodtarget = essentials × months; time = target ⁄ saving Worked example £1,800/mo × 4 · saving £300 £7,200 · 24 months
  3. 06 Overpay vs invest The kitchen-table classic: the same monthly money against the mortgage or into the market, side by side. Methodinterest saved at m% vs FV at r%, same £ Worked example £200/mo · 4.5% mortgage · 5% return · 20y +£4,100 investing
Calculator Retirement § 03
  1. 07 Retirement gap Project your pension pot to retirement age and compare it with the pot a target income would typically need. Methodneed = income ÷ withdrawal rate; gap = need − FV(pot) Worked example £85k pot · £400/mo · 30y · target £30k/yr gap £182,000
  2. 08 Pension tax relief What a monthly contribution really costs you after tax relief — and what lands in the pot with an employer match. Methodnet cost = gross × (1 − marginal rate) Worked example £400 gross · basic rate costs you £320
  3. 09 Drawdown sustainability How long could a pension pot last? Model withdrawals, growth and inflation and find the depletion age. Methodpotₜ₊₁ = potₜ(1+r) − w(1+i)ᵗ until pot ≤ 0 Worked example £300k · £18k/yr · 4% · 2.5% inflation lasts to age 89
  4. 10 State Pension top-up The payback maths on buying voluntary National Insurance years — often the best deal in UK finance. Methodpayback = cost ÷ (annual uplift) Worked example £824 for one year · +£328/yr pays back in 2.5 years
Calculator Property § 04
  1. 11 Mortgage repayments Monthly payments and total interest for any loan, rate and term — plus the effect of regular overpayments. MethodM = P · r(1+r)ⁿ ⁄ ((1+r)ⁿ − 1) Worked example £250,000 · 25y · 4.5% £1,390 / month

About these tools: results are illustrative projections based on the assumptions you enter — they are not forecasts, guarantees, advice or personal recommendations. Real returns vary and capital invested is at risk. For decisions, consult an FCA-authorised adviser.