ToolsJapanese knife calculators
and interactive tools

Two calculators answer the two numbers people ask us most: what a knife ordered from Japan really costs in the US once duty is added (about 31.1% for a wooden handle as of 2026-10-21), and how high to lift the spine off the whetstone for a given angle (11.6 mm for a 45 mm-tall blade at 15° per side). Both work in the browser, need no sign-up and show the formula they use.

Calculators

  • US import duty calculator — enter the yen price, quantity, shipping and exchange rate to see the regular duty (6.1% + 0.4¢ per knife under HTS 8211.92.90.30), the 25% Section 232 steel tariff and a typical carrier fee, then compare the landed cost with a US shop price. Worked examples and the tariff sources are on the page.
  • Sharpening angle & spine-height calculator — enter the blade height and the angle per side to get the spine gap in millimetres and as a stack of US pennies or ¥10 coins, with a reference table for common blade heights and recommended angles for each Japanese knife type.

Interactive tools on the home page

  • Knife finder — 8 Japanese knife shapes drawn to one scale, with bevel, typical length and use.
  • Steel explorer — pick up to three of 15 steels and compare carbon, chromium, maker hardness and CATRA edge retention.
  • Edge-angle viewer — a cross-section of single- and double-bevel edges from 8° to 25° per side.
  • Landed-cost calculator — a quick version of the duty calculator that puts buying from Japan next to buying from a US retailer.
Sharpening a kitchen knife on a water-cooled grinding wheel
The sharpening calculator turns an angle into a spine height you can hold on the stone. AI-generated illustration.

How the numbers are worked out

The duty calculator multiplies the value of the knives by the regular rate for the handle material and adds the Section 232 rate on the full value, because kitchen knives are listed as steel derivative articles; the US–Japan 12.5% rate does not apply to them. It treats the price you enter as the customs value and leaves shipping out of the dutiable amount, which is a simplification — check your carrier’s invoice. Tariffs change often, so the page shows the date we last checked every rate against the US tariff schedule and the proclamations.

The sharpening calculator uses plain trigonometry: spine gap = blade height × sin(angle). That holds for a double-bevel knife held flat to the stone at the spine. On a single-bevel knife you lay the bevel itself on the stone, so treat the result as a guide to the angle rather than a height to hold. Coin stacks use 1.52 mm for a US penny and 1.5 mm for a ¥10 coin.

Related guides

The calculators pair with the guide to buying a Japanese knife from Japan (shipping, carry-on rules and Japan’s tax refund from November 1, 2026) and with single-bevel vs double-bevel, which explains why the two edge types are sharpened differently. To choose a steel before you calculate anything, start from the steel chart or the comparisons.