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Calculators that show their working.

Every tool on numlane uses the current official rates, shows the formula, links the source and lets you download the result. Your inputs stay in your browser.

Selling online

eBay Fee Calculator (US)Final value fee by category, per-order fee, promoted listings and your profit after every fee.eBay Fee Calculator UKPrivate vs business sellers, the buyer protection fee, VAT on fees and what you keep.

AI & developers

LLM Token Counter & API Cost CalculatorCount tokens for GPT, Claude and Gemini in your browser and price a prompt across models.

Auf Deutsch

DEVerzugszinsen-RechnerTaggenau nach § 288 BGB, mit Basiszinssatz-Wechseln, Teilzahlungen, 40-€-Pauschale und Mahnschreiben.DEBasiszinssatz aktuellAktueller Basiszinssatz nach § 247 BGB, alle Werte seit 2002 und die Verzugszinssätze daraus.

How numlane works

Sourced rates. Fees, interest rates and prices come from the official pages, with the date they were last checked shown on every tool.
Visible formulas. Each page explains the calculation and works through an example you can reproduce by hand.
Downloads. Export the result as a spreadsheet with live formulas, a CSV, or a printable letter where it helps.
Private by default. Calculations run in your browser. Analytics load only if you allow them.