---
title: "Size of a Rice Grain: Millimeter Scale, Short vs. Long Grain & Anatomy | RiceHearth"
description: "Exact size of a rice grain in mm and inches (4.8 to 8.0 mm, 20 to 27 mg), interactive US penny scale, grain counts per cup, and short vs. long grain guide."
canonical: "https://ricehearth.com/size-of-rice-grain/"
author: "Mom of two boys, cooking rice for over 30 years"
disclosure: "Reader-supported: As an Amazon Associate I earn from qualifying purchases."
---

# Size of a Rice Grain: Exact Dimensions, Visual Scale & Short vs. Long Grain Guide

The size of a rice grain ranges from 4.8 to 8.0 millimeters long (0.19 to 0.31 inches) and 1.8 to 3.0 millimeters wide when dry, weighing 20 to 27 milligrams per kernel. In everyday terms, laying three long grains end to end (21 mm) spans the width of a US penny (19.05 mm), and a single 180 ml Japanese *go* cup holds about 6,500 to 7,200 grains of rice. Below are my true-to-scale visual diagrams, an interactive grain-count and scale simulator, botanical kernel anatomy, and how short, medium, and long grains behave in my rice cooker.

Open Interactive Scale & Grain Counter   Open Water Ratio Visualizer
![Cooked white short-grain rice inside my black Zojirushi NL-EAC18 B683 inner pot with white water markings](/images/editorial/black-pot-water-lines.webp)
*Cooked white rice inside my Zojirushi NL-EAC18BA B683 pot. A dry 5.3 mm Japonica grain swells plump to ~7.5 mm when steamed.*

Dry Kernel Length   5.0 to 8.0 mm   0.20" (Sushi short) to 0.31" (Aged Basmati) • Width: 1.8 to 2.9 mm       Single Grain Weight   20 to 27 mg   0.020 to 0.027 grams dry • Swells to ~55 to 65 mg when steamed       Grains in 1 Go Cup (180 ml)   ~6,500 grains   ~150 g dry rice • A 240 ml US cup (~200 g) holds ~8,700 grains       Penny Scale Benchmark   3 Grains = 1 Penny   US penny is 19.05 mm wide • 3 Jasmine grains end-to-end = 21.0 mm
## Interactive Rice Grain Scale & Cup Grain-Count Calculator

Pick a rice variety and a kitchen scoop size below to compare its raw vs. cooked millimeter dimensions against a US penny (19.05 mm) and see how many individual grains sit inside your pot.

1. Select Rice or Grain Variety:        2. Select Scoop or Batch Volume:
Japanese White Short-Grain (5.3 × 2.8 mm) vs. US Penny (19.05 mm)

Drawn to exact proportional millimeter scale (1 mm = 11 px)
15 mm   10 mm   5 mm   0 mm               US PENNY EDGE (19.05 × 1.52 mm)
3.6 dry grains end-to-end = 1 US Penny (19.05 mm)
US Penny Width = 19.05 mm (0.75 in)            5.3 × 2.8 mm   1 Dry Grain            7.4 × 3.8 mm   1 Cooked Grain      38.5px tall x 19.8px wide) -->       3.5 × 1.8 mm   Sesame Seed      r=11px) -->       2.0 mm disc   Quinoa Seed                 Estimated Individual Grains   ~6,820 grains   at 22.0 mg per dry kernel (150 g total)       Length-to-Width & Starch Class   1.9 : 1 (Short)   ~15% amylose / 85% amylopectin       Cooked Swell Expansion   7.4 × 3.8 mm   Swells plump widthwise • 1 : 1.15 water       Laid End-to-End Line Length   36.1 meters (118 ft)   If every grain in your scoop lined up
## What Each Rice & Grain Looks Like: Visual Identification Guide

Before you measure water, look closely at the dry grain in your scoop. A grain's physical shape (length-to-width ratio), outer bran coat, and translucency tell you how much water it will drink inside a sealed rice cooker.

*Shorter, rounder Japonica kernels (left) are rich in branched *amylopectin* starch and need less water (1 : 1.05–1.15) so they don't burst into mush. Longer, slender Indica kernels (right) carry higher linear *amylose* starch and drink more water (1 : 1.25–1.40) to elongate cleanly.*

Short / Medium Japonica & Sushi   5.0–5.5 mm • Oval Glassy Pearl
Raw kernels look plump, oval, and semi-translucent like frosted glass with a tiny notch at one tip where the germ was polished away. Cooks up glossy and clingy enough to lift in neat clumps with chopsticks.

Jasmine vs. Aged Basmati   7.0–8.0 mm • Slender & Needle-Thin
Jasmine (left kernel) is 3.5× longer than wide with softly rounded tips and a floral aroma. Aged Basmati (right kernel) is sword-thin (4.5:1 ratio) with sharp pointed ends and a golden-ivory hue that doubles in length when steamed.

Brown (Genmai) & Sprouted GABA   5.5 mm • Tan Bran + Golden Germ
Wrapped in its tan-amber outer bran (*nuka*) with a darker golden germ at the tip. When soaked on the GABA Brown cycle, a tiny pale-cream sprout visibly emerges from the germ tip, softening the chew.

Quinoa (Popped Germ Spirals)   2.0 mm • Round Disc + White Tail
Tiny flat-round seeds (ivory, red, or black). You know quinoa is perfectly cooked at a 1 : 1.35 ratio when the translucent center turns fluffy and the white germ ring uncurls like a tiny spiral halo around each seed.

## Inside a Grain of Rice: Botanical Anatomy & Japanese Milling Stages

When rice comes out of the field as rough paddy rice (*momi* / `籾`), each kernel is wrapped in a hard, inedible protective hull that accounts for about 20% of its weight. Once that outer hull is removed, you are left with whole-grain brown rice (*genmai* / `玄米`). How much of the outer bran and germ the mill polishes away determines both the size of the grain and which button you press on your rice cooker.

*Notice the tiny scoop-shaped dent at the bottom-left tip of a polished white *Hakumai* grain: that notch is the exact socket where the golden *Haiga* embryo sat before milling. Also notice how *Uruchimai* table rice looks glassy and semi-translucent, whereas *Mochigome* sweet rice looks solid chalk-white because its starch is 100% branched amylopectin.*

Reviewer's note: How grain texture and sushi rice behave in my Zojirushi NL-EAC18BA:
Because my family eats white rice almost every day, I cook short-grain white rice almost daily in my [Zojirushi NL-EAC18BA](/reviews/zojirushi-nl-eac18/), and I have also tried other grains and menus with very good results. When I make vinegared sushi rice (*sumeshi* / `酢飯`), filling water to the dedicated `SUSHI` line inside the black pot uses slightly less water so the grains come out a touch firmer, which is just right for folding in rice vinegar without turning soft. On regular everyday white rice, the flavor comes out delicious, though on my Micom cooker I feel the grains do not quite get that look where every single grain stands up distinctly (`1粒1粒が立ち上がる感じ`) or has a super glossy-smooth outer surface (`つるんとした感じ`); the outside of the grain feels slightly rougher, which can also depend on the rice brand you buy.

## Short-Grain vs. Medium-Grain vs. Long-Grain Rice: Dimensions, Starch & Cooking Chart

Both the USDA and the UN Codex Alimentarius sort rice into size classes using two physical measurements: raw kernel length in millimeters and the length-to-width aspect ratio. However, what you actually taste on your plate comes down to the ratio of two starches inside the endosperm: linear *amylose* (which makes grains cook up firm, dry, and separate) and branched *amylopectin* (which makes grains swell wide, glossy, and sticky).

| Rice Variety & Class | Dry Size (L × W) | L:W Ratio | Cooked Size | 1,000-Grain Wt | Amylose / Amylopectin | Cooked Texture & Best Dishes | Cooker Water Ratio (per 180ml go) |
| --- | --- | --- | --- | --- | --- | --- | --- |
| **Sushi Short-Grain** (e.g., Sasanishiki) | 5.0 × 2.9 mm (0.20" × 0.11") | 1.7 : 1 (Short) | 7.0 × 3.9 mm | ~21.5 g (21.5 mg/grain) | 14% / 86% | Plump, glossy pearls that hold vinegar without splitting; nigiri, maki rolls, chirashi | 1 : 1.05 (SUSHI line) |
| **Japanese White (Hakumai)** (e.g., Koshihikari) | 5.3 × 2.8 mm (0.21" × 0.11") | 1.9 : 1 (Short) | 7.4 × 3.8 mm | ~22.0 g (22.0 mg/grain) | 15% / 85% | Soft, sweet, springy cling that lifts cleanly with chopsticks; daily bowls, onigiri, bento | 1 : 1.15 (WHITE line) |
| **Glutinous Sweet (Mochigome)** (もち米 / Sticky) | 5.1 × 2.9 mm (0.20" × 0.11") | 1.8 : 1 (Short) | 6.9 × 4.0 mm | ~21.0 g (21.0 mg/grain) | 0% / 100% | Opaque chalk-white raw; cooks into stretchy, dense sticky rice for mochi, sekihan, zongzi | 1 : 1.00 (Sweet line) |
| **California Calrose** (Medium-Grain Japonica) | 5.8 × 2.5 mm (0.23" × 0.10") | 2.3 : 1 (Medium) | 8.4 × 3.4 mm | ~23.5 g (23.5 mg/grain) | 17% / 83% | Tender, moist, slightly less sticky than short-grain; poke bowls, everyday table rice | 1 : 1.15 (WHITE line) |
| **Arborio / Carnaroli** (Italian Medium Bold) | 6.2 × 3.1 mm (0.24" × 0.12") | 2.0 : 1 (Medium) | 9.0 × 4.3 mm | ~28.5 g (28.5 mg/grain) | 16% / 84% | Fattest kernel with a chalky center core (*al dente*) that sheds creamy surface starch; risotto, rice pudding | Stovetop broth ladle or 1 : 1.25 |
| **US Long-Grain White** (Indica) | 6.6 × 2.1 mm (0.26" × 0.08") | 3.1 : 1 (Long) | 10.6 × 2.7 mm | ~24.0 g (24.0 mg/grain) | 24% / 76% | Fluffy, drier, distinct separated grains that do not clump; pilaf, stir-fry, gumbo, burrito bowls | 1 : 1.30 (LONG GRAIN line) |
| **Thai Hom Mali Jasmine** (Aromatic Long) | 7.0 × 2.0 mm (0.28" × 0.08") | 3.5 : 1 (Long) | 11.2 × 2.6 mm | ~23.0 g (23.0 mg/grain) | 18% / 82% | Slender, floral aroma (natural 2-AP compound), softer and slightly more cohesive than US long-grain; curries, Thai dishes | 1 : 1.25 (JASMINE line) |
| **Aged Indian Basmati** (Extra-Long Grain) | 8.0 × 1.8 mm (0.31" × 0.07") | 4.5 : 1 (Extra-Long) | 15.2 × 2.3 mm | ~21.5 g (21.5 mg/grain) | 26% / 74% | Sword-thin golden-ivory needle that stretches nearly 2× longer when steamed; biryani, pulao | 1 : 1.40 (Long/White menu) |
| **Whole-Grain Brown (Genmai)** (Unmilled Short/Med) | 5.5 × 2.8 mm (0.22" × 0.11") | 2.0 : 1 (Whole) | 7.6 × 3.8 mm | ~24.5 g (24.5 mg/grain) | 15% / 85% + bran | Nutty, chewy outer bran layer with intact golden germ bud; hearty bowls, macrobiotic plates | 1 : 1.55 (BROWN line) |

## Why Grain Size and Starch Dictate Which Rice Cooker Menu You Press

If you swap short-grain rice for long-grain rice without changing your water level or menu preset, the batch comes out wrong because the two grains absorb water along completely different physical paths:

- **Short-grain Japonica (5.0 to 5.5 mm) needs a warm pre-soak and less water (1 : 1.05 to 1.15):** Because plump oval kernels have a lower surface-area-to-volume ratio and 85%+ branched amylopectin starch, water takes 15 to 20 minutes to reach the center core. Micom and Induction cookers like my [Zojirushi NL-EAC18BA](/reviews/zojirushi-nl-eac18/) automatically hold the water warm before boiling so the core gelatinizes without drowning the outside in extra water.
- **Long-grain Indica (6.6 to 8.0 mm) drinks more water (1 : 1.25 to 1.40) and elongates lengthwise:** Slender Jasmine and Basmati kernels have a thinner cross-section (1.8 to 2.0 mm wide) and higher linear amylose starch, which requires more water and a higher gelatinization temperature to stretch out to 11 to 15 mm without snapping. That is why having a dedicated `JASMINE` and `LONG GRAIN WHITE` button on the NL-EAC18BA prevents dry, chalky centers.
- **Unmilled Brown Genmai (5.5 mm with intact bran) needs a 60-to-90-minute cycle (1 : 1.55):** The waxy outer *nuka* bran coat repels cold water. If you cook brown rice on a 45-minute White Rice cycle, the bran splits open while the center stays hard. The `BROWN` and `GABA BROWN` settings hold the pot at a gentle pre-soak temperature so moisture penetrates the microscopic germ pore before boiling.
- **New-Crop Rice (*Shinmai* / `新米`) vs. Older-Crop Rice (*Komai* / `古米`):** Freshly harvested autumn *Shinmai* kernels carry about 15% internal moisture, whereas stored rice drops toward 12% to 13%. When cooking fresh *Shinmai*, I fill water just a hair (1 to 2 mm) below the pot line so the rice does not turn overly soft.

Want to convert exact cup and millimeter water levels for your specific grain? Open my [Interactive Rice-to-Water Ratio Visualizer](/tools/rice-to-water-ratio-calculator/) or follow my [5-Step Rice Cooker Routine](/guides/how-to-cook-rice-in-a-rice-cooker/).

## Common Questions

### How big is a single grain of rice in millimeters and inches?

An uncooked grain of milled white rice measures 4.8 to 8.0 millimeters long (0.19 to 0.31 inches) and 1.8 to 3.0 millimeters wide, depending on variety. Japanese short-grain sushi rice averages 5.0 x 2.9 mm (1.7:1 length-to-width ratio), medium-grain Calrose averages 5.8 x 2.5 mm (2.3:1), Thai Jasmine averages 7.0 x 2.0 mm (3.5:1), and aged Basmati reaches 8.0 x 1.8 mm (4.5:1). Three long grains laid end to end (21 mm) are just slightly wider than a US penny (19.05 mm).

### How much does one grain of rice weigh, and how many grains are in a cup?

One grain of dry white rice weighs 20 to 27 milligrams (0.020 to 0.027 grams), based on a 1,000-kernel weight of 20 to 27 grams. A 180 ml Japanese rice cooker cup (1 go, about 150 grams of dry rice) holds roughly 6,000 to 7,500 individual grains. A standard 240 ml US measuring cup (about 200 grams) holds 8,000 to 10,000 grains, and 1 kilogram holds 37,000 to 50,000 grains.

### What is the difference between short-grain, medium-grain, and long-grain rice?

Grain classes are defined by both length-to-width ratio and starch chemistry (amylose vs. amylopectin). Short-grain rice (under 5.5 mm long, under 2:1 ratio) has low amylose (12% to 15%) and high branched amylopectin (85% to 88%), so it swells plump and clings together for chopsticks and sushi. Medium-grain rice (5.5 to 6.5 mm, 2:1 to 2.9:1 ratio) has 15% to 19% amylose for a tender, creamy bite. Long-grain rice (6.6 to 8.0+ mm, 3:1 to 4.5:1 ratio) has high linear amylose (20% to 28%), so it stretches lengthwise and stays fluffy and separate.

### What is the difference between Japanese Uruchimai and Mochigome rice?

Uruchimai (うるち米) is ordinary Japanese short-grain table rice (~15% amylose, ~85% amylopectin), which looks glassy and semi-translucent when raw. Mochigome (もち米) is Japanese glutinous sweet rice (0% amylose, 100% amylopectin), which looks opaque chalky-white when raw and steams into a stretchy, cohesive dough for mochi and sekihan.

## 📌 Cite This Kitchen Hardware & Measurement Reference

Primary-Source Verified (2026-10-12)
Food writers, journalists, and community moderators (Reddit `r/Cooking`, `r/ricecookers`, `r/BuyItForLife`) are welcome to reference or link to my 180 ml Japanese *go* (合) vs. 240 ml US cup conversions, detachable inner-lid audit, and manufacturer wattage tables with attribution to RiceHearth.

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