Calculate a tip and split the bill
Drop in the bill, pick a tip percent, set the party size — see the tip amount, total, and per-person split update live. Runs entirely in your browser.
Tip = bill × tip%. Total = bill + tip. Per-person divides both by party size.
How to split a check
Pick a tip percent based on service; the calculator shows both the tip alone and the bill with tip, plus what each person owes.
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Enter bill
Type the pre-tax bill amount.
Inputs are treated as UTF-8 throughout the pipeline and validated client-side as you type — nothing dispatches until the value is well-formed.
billinpututf-8client-sidevalidatedbill · text$50 · set$50.00
loaded · parsedclient-side - 02
Pick tip %
Quick chips for 10/15/18/20/25 or any value 0-30 on the slider.
Each toggle re-computes through a memoised hook, so flipping options never resets your input and the UI stays snappy on large inputs.
tipoptionslivememoisedtogglestip · memoised18% · livetip $9.00
options set · memoisedlive - 03
Set party size
How many ways to split the total.
Randomness — where used — comes from
crypto.getRandomValues, neverMath.random. Heavy work sits inuseMemo.splitcomputeinstantlocaldeterministicparty · instant2 · computedsplit 2 ways
computed · instantinstant - 04
Read result
Tip, total, per-person tip, per-person total update live.
Copy writes through
navigator.clipboardand downloads use aBlob— zero network traffic. Same input plus same options always yield the same bytes.livecopydownloadzero-networkreproducibleok · copiedready · copied$29.50 / person
shipped · ready to shipsuccess
Pro tips for everyday utilities
Reach for crypto.getRandomValues
Cryptographically random for IDs, tokens, salts. Math.random is for animation and games, not security.
Mock data with seeds
Faker-style libraries can be seeded so tests are reproducible. Embed the seed in the fixture file.
Reference cards beat memory
Cheatsheets for Vim, Git, Docker, Linux signals are faster than man pages when you’re mid-flow.
Browser APIs vary
Touch events, gamepads, and clipboard differ across vendors. Feature-detect before use.
Persist in the right place
localStorage for user preferences, sessionStorage for transient state, IndexedDB for structured data.
When to compute a tip
Restaurants, group dinners, rideshare.
Restaurant bills
Standard 18-20% on the pre-tax total. Random values come from crypto.getRandomValues — cryptographically secure for tokens, salts, and session IDs. Math.random is deterministic enough for animations but predictable enough to be a security bug.
CSPRNG-backedGroup dinners
Split evenly when everyone agrees. Pair with hashids, ULID, or UUID v7 when you need both random and sortable — useful for primary keys, public-facing IDs, and event log ordering without a sequence column.
reproducibleRideshare
Quick tip on a ~$15-30 ride. Output is deterministic given the same seed, so fixtures and tests stay reproducible across CI runs and contributor machines. Embed the seed in the fixture file for full replay.
snappyBar tabs
Per-round tip plus a closing total. Heavy work runs through useMemo so the UI stays snappy on large inputs. Same input + same options yields identical bytes — the kind of stability snapshot tests rely on.
feature-detectedTravel
Faster than mental math in unfamiliar currencies. Storage tools persist to the right backend: localStorage for user preferences, sessionStorage for transient state, IndexedDB for structured data. Pick the right shelf and quota worries disappear.
deterministicService workers
Hair, nails, delivery — anywhere a tip applies. Browser feature detection: clipboard, fullscreen, gamepad, and Web Bluetooth APIs gracefully fall back when unavailable. No surprise white screens on Safari or older Firefox.
production-readyFrequently asked questions
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