Free calculator · US & UK
Savings vs CD vs Treasury bills: where should cash sit?
The short answer: easy-access savings for money you might need, fixed terms for money with a date on it, and government bills when state tax or safety at size matters. This tool prices all three after tax at your own rates so the decision stops being a vibe.
High-yield savings in the US, easy-access in the UK. Variable: it follows the central bank down, which is the hidden cost of flexibility in a rate-cut cycle.
Locked for the term. You are paid to give up access; early exit usually costs months of interest.
4 to 52 week government paper. In the US, T-bill interest is exempt from state income tax, which flatters the after-tax number in high-tax states.
US: your marginal federal (plus state, except on T-bills). UK: 0% inside the personal savings allowance or an ISA, then your income tax band.
The honest reading: over 12 months the spread between your best and worst option is $62, which tells you whether shopping harder is worth an afternoon. Three rules that outlive any rate table. Emergency funds live in easy access, full stop; a locked emergency fund is an oxymoron. Fix only money with a date on it. And in a falling-rate cycle the fixed option is quietly buying insurance against the easy-access rate melting, which is worth more than the headline gap suggests.
All three end values at your rates, saved.
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Educational information, not financial advice. Figures current as of July 2026 where dated; allowances and rates change, so check the source before acting.