What resistor values should I use?

Trade-off: small values = better load tolerance but high quiescent current (battery drain); large values = low quiescent current but more loading sensitivity. For 5 V → 3.3 V level shift powering a high-impedance MCU pin: R1=R2=10 kΩ is fine.

Can I use a divider as a voltage REGULATOR?

No — voltage dividers have no regulation. V_out scales with V_in and sags with load. For regulation use a linear regulator (LM7805 etc.) or switch-mode buck converter.

Horowitz & Hill "The Art of Electronics" 3rd ed Ch. 1.2; National Semiconductor / TI app notes on voltage-divider design.

What resistor values should I use?

Trade-off: small values = better load tolerance but high quiescent current (battery drain); large values = low quiescent current but more loading sensitivity. For 5 V → 3.3 V level shift powering a high-impedance MCU pin: R1=R2=10 kΩ is fine.

Can I use a divider as a voltage REGULATOR?

No — voltage dividers have no regulation. V_out scales with V_in and sags with load. For regulation use a linear regulator (LM7805 etc.) or switch-mode buck converter.

Horowitz & Hill "The Art of Electronics" 3rd ed Ch. 1.2; National Semiconductor / TI app notes on voltage-divider design.

Voltage Divider Calculator

Vout = Vin · R2 / (R1 + R2). Solve for any one of Vin/R1/R2/Vout given the other three.

Result

V_out

8.2500 V

Divide ratio R2/(R1+R2) = 0.6875. Current 3.750 mA.

V_in12.0000 V
R11,000.00 Ω
R22,200.00 Ω
V_out (no load)8.2500 V
Divide ratio0.68750
Current through divider3.7500 mA (= V_in / (R1+R2))
Power in R114.0625 mW
Power in R230.9375 mW
Total dissipation45.0000 mW

Step-by-step

Voltage-divider formula: V_out = V_in · R2 / (R1 + R2).
12 · 2200 / (1000 + 2200) = 8.2500 V
No-load condition (R_load = 0/∞ ignored).

How to use this calculator

Pick the unknown — V_out is the most common; R1/R2 modes solve for a needed resistor value.
Enter V_in (supply voltage), R1 (top resistor), R2 (bottom resistor).
If your divider feeds a real load (microcontroller pin, op-amp input, etc.), enter the load impedance to see the sagged V_out.

About this calculator

A voltage divider is two resistors in series with the output taken at the midpoint. V_out = V_in · R2 / (R1 + R2) — the unloaded transfer function. The classic failure: forgetting that any LOAD draws current through R2 in parallel, reducing the effective R2 and dropping V_out below the no-load prediction. Rule of thumb: the divider current (V_in / (R1+R2)) should be 10-100× larger than the load current, or use a buffer (op-amp follower). For voltage references requiring precision, use a Zener diode or dedicated reference IC instead — voltage dividers have no inherent regulation and shift with V_in. The tool models both ideal (no-load) and loaded cases; toggle loadR > 0 to see the sag.

Frequently asked

The load resistance shunts R2 in parallel, reducing the effective bottom-leg resistance. Loaded V_out = V_in · (R2 || R_load) / (R1 + R2 || R_load), always LESS than the no-load value.