Grout Knife: Complete Guide for Homeowners

A grout knife is the cheapest, most controllable tool for digging old grout out from between tiles, and for a lot of small repair jobs it’s all you actually need. At $8 to $25 it costs less than a takeout dinner, yet used correctly it lets you regrout a shower or refresh a floor line without the noise, dust, and risk of power tools.

Part of our Tile & Grout guide — explore the full guide →

I’ve regrouted more bathrooms than I can count, and the tool choice always comes down to the size of the job and how much control you need near fragile tile edges. This guide covers the manual hand tools, when a power tool earns its place, and the technique that keeps you from chipping the tiles you’re trying to save.

What a Grout Knife Actually Is

Despite the name, a grout knife isn’t sharp like a kitchen knife. It’s a handled tool with a hardened, often carbide-tipped blade designed to scrape and score the hard cementitious grout lines between tiles. Some have a straight blade, others a hooked or angled tip that pulls grout toward you as you drag it.

The carbide tip is the important detail. Cheap versions use plain steel that dulls in one bathroom, while a carbide-grit blade holds an edge through many linear feet of grout. Spend the extra few dollars for carbide — it’s the difference between a frustrating afternoon and a tool that keeps cutting.

The Manual Grout Tools and When to Use Each

There’s a small family of hand tools for this work, and each has a job it does best.

Grout knife or grout saw

Best for detail work and short runs — cracked grout in a corner, a few feet of a shower seam, or getting into tight spots a power tool can’t reach. It gives you total control, so it’s the safest choice around delicate glass tile, mosaic, or antique tile you can’t easily replace.

Grout rake

A grout rake has a wider, often replaceable carbide blade and is built for raking out longer, straighter runs of grout on floors and walls. It removes material faster than a knife but demands a steady hand to stay centered in the joint. Many models let you swap in wider or narrower blades to match your grout line.

Reciprocating hand tool with a hook

Some carbide hook tools are meant to be pulled hard in short strokes. They bite aggressively, which is great on wide joints but easy to overdo on narrow ones. Match the blade width to your grout line — never force a wide blade into a thin joint.

When to Reach for an Oscillating Multi-Tool

Once a job crosses roughly 15 to 20 linear feet, manual removal starts to wear out your hand and your patience. That’s when a power tool earns its keep.

An oscillating multi-tool — the kind sold by Fein, Bosch, Dewalt, or Milwaukee — accepts a carbide or diamond grout-removal blade and vibrates at high speed to grind grout out fast. A Dremel rotary tool with a dedicated grout-removal attachment and guide is another popular option for tighter, more precise work. Both cut grout in a fraction of the time a knife takes.

The trade-off is dust and risk. Power tools throw a lot of fine silica dust, so wear an N95 respirator and eye protection and run a fan. They also chip tile far more easily than a hand tool if your hand slips, which is exactly why I still reach for a grout knife on the last pass near tile edges.

Technique: How to Avoid Chipping Tile Edges

This is the part that separates a clean job from a wrecked one. Chipped tile edges are almost always caused by the blade wandering out of the joint and into the glaze. Here’s how to keep that from happening.

• Stay centered. Keep the blade in the middle of the grout line and let it ride the joint. The grout is softer than the tile, so a centered blade cuts grout and glances off tile.
• Score first, dig second. Make several light passes to score a channel down the center before you try to remove full depth. Light passes give you control; heavy digging invites slips.
• Pull, don’t gouge. With a hooked knife, drag toward yourself in controlled strokes rather than levering sideways against a tile.
• Leave a thin margin. Get within a hair of the tile with the power tool, then switch to the hand knife to clean the last sliver right up against the edge.
• Don’t dig deeper than you need. Remove grout to at least two-thirds of the depth or down to the tile substrate, but you don’t need to excavate to the backer board.

The Full Regrouting Workflow

Removing grout is step one of a larger job. Here’s how the whole thing flows so you’re not caught off guard.

1. Remove the old grout to a consistent depth using your knife, rake, or oscillating tool.
2. Vacuum every joint thoroughly — a shop vac with a crevice tool pulls out the dust and crumbs that keep new grout from bonding.
3. Wipe the tile faces with a damp sponge and let everything dry completely.
4. Mix and apply new grout, forcing it fully into the joints at a 45-degree angle with a rubber float.
5. Wait 10 to 20 minutes, then wipe the haze with a barely damp sponge, rinsing often.
6. Let it cure per the bag — usually 24 to 72 hours — before sealing and before exposing it to water.

Don’t skip the vacuuming. New grout bonds to clean joints; it crumbles out of dusty ones within months.

What It All Costs

The budget here is genuinely small. A manual grout knife or saw runs $8 to $15, and a decent carbide grout rake with replaceable blades runs $15 to $25. If you already own an oscillating multi-tool, a carbide grout blade is $15 to $30; a full Dremel grout kit is $30 to $50. A bag of grout is $15 to $30, and grout sealer another $15 to $25.

All in, a small regrouting job done by hand can cost under $60. Even adding a power tool blade keeps most bathroom refreshes well under $150 in materials — a fraction of what a tile contractor would charge for the same work.

Sanded vs. Unsanded: Match the New Grout to the Joint

Once the old grout is out, don’t grab the first bag on the shelf. The joint width dictates which grout goes back in. For joints wider than 1/8 inch — most floor tile — use sanded grout, which resists shrinking and cracking in wide seams. For narrow joints of 1/8 inch or less, common on polished wall tile and glass mosaics, use unsanded grout so the sand doesn’t scratch delicate faces.

Match the color too. Grout is sold in dozens of shades, and even a “matching” white can read noticeably brighter or grayer than the aged grout you’re leaving in place elsewhere. If you’re only regrouting part of a wall, bring a chip of the old grout to the store, or plan to redo the whole area for a uniform look.

Safety and Dust Control

Old grout dust contains crystalline silica, and cutting it releases fine particles you should not breathe. Whether you go manual or powered, wear an N95 or better respirator, safety glasses, and gloves. Power tools make far more dust than a hand knife, so on those jobs run a fan blowing away from you, open a window, and consider a dust-collection shroud if your oscillating tool accepts one. Wipe surfaces down with a damp cloth afterward rather than dry-sweeping, which just kicks the dust back into the air.

Choosing the Right Approach for Your Job

Match the tool to the scope. For a few cracked joints or delicate tile, a hand grout knife gives you the control you want and costs almost nothing. For a full floor or a whole shower surround, start with an oscillating tool for speed and finish the edges by hand. Either way, the carbide blade, a centered stroke, and a slow scoring pass are what protect your tile and get you a clean, professional-looking result.