Under $100 means a pen tester. The cheapest pens read to ±0.1 pH, but a few in this range reach ±0.01 pH, accept three-point calibration and take a replacement probe.
Prices were last checked November 9, 2026. Product prices and availability are accurate as of that date and are subject to change; the price and availability shown on Amazon or the retailer's site at the time of purchase apply. As an Amazon Associate we earn from qualifying purchases.
Best pH Meters Under $100: Pen testers
- Apera PH60#1 of 5Full review
The pick for most people who want an accurate pen tester: ±0.01 pH, three-point calibration and a replaceable probe at pen-tester money.
Amazon $79.99$79.99±0.01 pH3-pointNone - VIVOSUN AeroLab pH Pen#2 of 5Full review
A low-cost grower’s pen with a replaceable probe. Its maker publishes little beyond the accuracy claim.
Amazon $65.99$65.99±0.01 pH-None - Apera PH20#3 of 5Full review
A cheap, waterproof pen for pools, aquariums and drinking water. Pick it when 0.1 pH is close enough.
Amazon $56.65$56.65±0.1 pH3-pointNone - Milwaukee pH55 Pro#4 of 5Full review
A low-cost pen with a replaceable electrode, for pools, gardens and aquariums. The Apera PH60 is more accurate for a little more.
Amazon $77.90$77.90±0.1 pH2-pointNone - Bluelab pH Pen#5 of 5Full review
A simple, tough pen for growers checking nutrient pH. The PenPlus costs a little more and adds a replaceable probe.
Amazon $89.95$89.95±0.1 pH2-pointNone
