For most homeowners checking a suspected leak, the Klein Tools ET140 is the meter to buy first: it’s pinless, so you can sweep drywall and floors without making holes, and Klein lists a sensing depth of about 3/4 inch. If your main job is wood, such as firewood, framing or a deck board, the General Tools MMD4E pin meter gives a moisture-content reading for about the same price. The General Tools MMD950 combines pin and pinless modes and reads deeper behind walls. The Tramex MEX5 is a professional survey tool that most homes don’t need.

No meter proves mold or finds the source of a leak. It tells you where material is wetter than a known-dry spot of the same kind, which is what you need before you open a wall or call a plumber.

Quick picks

Meter Best for Key specs (manufacturer or retailer) Price band
Klein Tools ET140 Scanning drywall, masonry and floors without holes Pinless; senses to 0.75 in.; drywall, masonry, hardwood and softwood modes; 0 to 100% relative scale; ±4% Under $50
General Tools MMD4E Wood moisture content on a budget Pin type; wood 5 to 50% WME, building materials 1.5 to 33%; ±2%; 0.3 in. pins Under $40
General Tools MMD950 One meter for both methods, deeper wall checks Pin (%WME) and pinless (relative) modes; pinless depth up to 4 in.; 46 in. remote pin probe $200 to $250
Tramex MEX5 (search) Professional moisture surveys Dual-depth pinless readings to about 3/8 in. and 1-1/4 in.; wood and building-material scales; optional pin and RH probes Third-party sellers only; over $1,000

Prices change daily. Treat them as a rough guide to the price tier, not a quote.

Klein Tools ET140: the first meter for most homes

Klein describes the ET140 as a nondestructive pinless meter that uses an electromagnetic field to read relative moisture up to 3/4 inch below the surface. A mode button switches between drywall, masonry, hardwood and softwood, and Klein says it’s calibrated for those four materials only. It has a reverse-contrast display with a nine-LED bar graph, a hold function, auto power-off, a 9V battery and a 6.6-foot drop rating.

Who it fits: anyone mapping a stain on a ceiling, checking the drywall around a tub or toilet, or comparing a basement wall with a dry wall nearby. Pinless meters cover area quickly, which is what a leak hunt needs.

Trade-offs: the reading is relative, not a lab-grade moisture content, and Klein lists ±4% accuracy. Metal behind the surface, such as corner bead, screws or foil-faced insulation, can raise readings. It also won’t read materials outside its four modes with any calibration.

General Tools MMD4E: a budget pin meter for wood

General Tools lists the MMD4E as a pin-type meter with two scales: wood from 5 to 50% WME (wood moisture equivalent) and building materials from 1.5 to 33%, with ±2% accuracy and 0.1% resolution. The pins are 0.3 inch long, the backlit display shows low, medium and high bands, and the pin cap doubles as a calibration check. It runs on a 9V battery and turns off after 3 minutes idle.

Who it fits: checking firewood, lumber before staining or finishing, subfloor plywood, or a deck board you suspect is rotting. A pin meter tells you the moisture at the pin tips, which is useful when you need a number for wood.

Trade-offs: every reading leaves two small holes, so it’s a poor choice for scanning a finished ceiling. Readings change with wood species, temperature and salts in the material, and a 0.3-inch pin only reads near the surface.

General Tools MMD950: pin and pinless in one meter

The MMD950 has two modes: pin, which reads %WME, and pinless, which gives a relative reading. The Amazon listing and a retailer spec sheet list pinless detection up to 4 inches behind walls and ceramic tile, a 46-inch remote probe cable with pins, a jumbo LCD plus a 40-dot tri-color bar graph, a hold function and a 9V battery. Penn Tool lists the pin range as 6.0 to 87.6% WME with ±3% accuracy in pin mode.

Who it fits: a homeowner dealing with a recurring problem, such as tile around a shower or a slab-level room, who wants to scan without holes and then confirm with pins in one spot.

Trade-offs: it costs about four to five times as much as either single-method meter. The deep pinless reading is relative, so it shows where to look, not how wet the material is. For a one-time leak check, the ET140 or MMD4E is usually enough.

Tramex MEX5: professional survey meter

Tramex lists two pinless depths for the MEX5, shallow to about 3/8 inch and deep to about 1-1/4 inches, which helps separate a surface event from a deeper pattern. It includes wood moisture (0 to 30% MC) and a 0 to 100 comparative scale for drywall, roofing, plaster, tile and masonry. It adds infrared surface temperature and dew-point calculations, and optional pin and relative-humidity probes extend it. Our Tramex MEX5 review covers the model in detail.

Who it fits: inspectors, restoration contractors, or a homeowner documenting a long-running problem for an insurer or contractor.

Trade-offs: price. On October 3, 2026 the Amazon listing was sold by a third-party seller at over $1,000, which is why the link above is a search.

How to choose

  • Pick pinless for finding, pins for measuring. Scan drywall and floors without holes, then use pins on wood when you need a number.
  • Always set a dry baseline. Read the same material in a spot you know is dry, then compare. One reading on its own tells you very little.
  • Map, don’t chase. Read above, below and to each side of a stain and mark the pattern with painter’s tape. A pattern that rises from the floor points to a different cause than one that spreads from a ceiling.
  • Stop active water first. A meter doesn’t replace shutting off a supply valve or calling for help with a roof leak, sewage or wet electrical areas.

If the damp area is on a basement wall, our guide to basement wall condensation vs. a leak explains how to tell them apart. For a musty smell with no visible stain, see finding a crawlspace musty-odor source . A thermal camera answers a different question; the FLIR Edge Pro review explains what surface-temperature images can and can’t show.

Sources

Checked October 3, 2026:

This page compares published specifications. No meter was tested for accuracy, and nothing here replaces a qualified inspection when water damage is extensive.