Guide collection
Tools
Free calculators and interactive tools from Rational GB.
No. 01
Investment Platform Fee Calculator UK: Percentage vs Flat Fee
Free UK investment platform fee calculator: enter your pot size and we work out the yearly cost on Trading 212, InvestEngine, Vanguard, AJ Bell, HL and interactive investor, ranked cheapest first.
Read guide
No. 02
Investment Growth Calculator UK: Project Your ISA or SIPP Pot
A UK investment growth calculator that projects your ISA or SIPP pot from a starting sum and monthly contributions, with fees and inflation deducted so you see the real, spendable value.
Read guide
No. 03
Pension Tax Relief Calculator UK: Basic, Higher and Additional Rate
A UK pension tax relief calculator that shows the real cost of a SIPP or pension contribution after 20% relief at source plus any higher or additional rate relief you claim back through Self Assessment.
Read guide
No. 04
How Long to Reach Your Investment Target: ISA and SIPP Time Calculator
Work out how long to reach 100k or any investment target, from your starting pot, monthly contribution and expected return, with the monthly amount that would get you there faster.
Read guideDividend Tax Calculator UK 2025/26: What You Owe on Your Dividends
A UK dividend tax calculator for 2025/26 that uses your other income to stack your dividends into the right bands, applies the 500 pound dividend allowance, and shows the tax due at 8.75, 33.75 and 39.35 percent.
Read guideCapital Gains Tax Calculator UK 2025/26: What You Owe on Shares and Funds
A UK Capital Gains Tax calculator for 2025/26 that deducts the 3,000 pound annual exempt amount, uses your other income to fill the basic rate band, and splits your gain across the 18 and 24 percent CGT rates for shares and funds.
Read guide