The Doubling Rule: What It Is and How to Teach It

By Lauren Kline, M.S., CCC-SLP, A/OGA, C-SLDI

Of the three major spelling/suffixing rules in English, the doubling rule is usually the one students learn first and the one that causes the most confusion when it's taught without the reasoning behind it. Once students understand why we double, the rule clicks.

The Rule

When a one-syllable word has one short vowel and ends in one consonant, double that final consonant before adding a suffix that starts with a vowel.

Some people call this the 1-1-1 rule: one syllable, one vowel, one final consonant. If all three conditions are met and the suffix starts with a vowel, you double.

How It Works

Take the word run. One syllable, one short vowel (u), one final consonant (n). Adding -ing:

• run + ing → running (not "runing")

More examples:

• stop + ed → stopped

• hop + ing → hopping

• sit + er → sitter

• big + est → biggest

• swim + ing → swimming

The consonant doubles every time because all three conditions are met and the suffix starts with a vowel.

Why We Double

This is the part most students never get taught, and it's the part that actually makes the rule stick.

We double to protect the short vowel sound.

Look at the difference between hopping and hoping. In "hopping," the double p keeps the o short. In "hoping," the single p after the long o tells the reader the vowel is long (because the silent e dropped -- that's the drop e rule working alongside this one).

Without doubling, "running" would look like "runing" -- and a reader following English spelling patterns would pronounce it with a long u, like "rooning." The double consonant is a signal: the vowel before me is short.

When NOT to Double

The rule only applies when all three conditions are met. If any one is missing, don't double:

Two vowels (vowel team):

• rain + ing → raining (not "rainning") -- the vowel is already long

Two final consonants:

• jump + ed → jumped (not "jumppped") -- the word ends in two consonants

Suffix starts with a consonant:

• sad + ness → sadness (not "saddness") -- consonant suffixes don't trigger doubling

More than one syllable (in a one-syllable context):

• open + ing → opening -- the stress isn't on the final syllable

Teaching the exceptions reinforces the logic. Students learn to check the conditions before applying the rule.

How to Teach It

1. Make sure students can identify short vs. long vowels. This is the foundation. If they can't hear or identify the vowel sound, the rule won't make sense.

2. Teach the 1-1-1 check. Before adding any vowel suffix, students ask three questions: One syllable? One vowel? One final consonant? If yes to all three, double.

3. Show the why. Write "hopping" and "hoping" on the board. Ask students to read both. Then ask: what's different? Why? Connect the doubling to the vowel sound it protects.

4. Word sorts. Give students a stack of base words and suffixes. Have them sort into "double" and "don't double" and explain their reasoning each time.

5. Contrast with the drop e rule. Once students know both rules, give them pairs like hop/hope + ing. They should be able to explain why one doubles and the other drops the e.

The Bigger Picture

The doubling rule, the drop e rule, and the change y to i rule are the three suffixing rules that govern most of English spelling. When students learn all three -- and understand the logic behind each they stop treating every new word as something to memorize. They start applying a system.

For SLPs working on morphology, written language, or multisyllabic word reading, these rules aren't optional extras. They're core knowledge that connects speech sounds to spelling patterns. And that connection is exactly where our work lives.

---

Lauren Kline is a speech-language pathologist and structured literacy specialist. She writes about the intersection of speech, language, and literacy at [lkslo.com](https://www.lkslo.com).