wc-min-order-amount.php

/**
 * Set a minimum order amount for checkout.
 */
function wb_wc_minimum_order_amount() {
	// Set this variable to specify a minimum order value.
	$minimum = 50;

	if ( WC()->cart->total < $minimum ) {

		if ( is_cart() ) {

			wc_print_notice(
				sprintf(
					'Your current order total is %s — you must have an order with a minimum of %s to place your order ',
					wc_price( WC()->cart->total ),
					wc_price( $minimum )
				),
				'error'
			);

		} else {

			wc_add_notice(
				sprintf(
					'Your current order total is %s — you must have an order with a minimum of %s to place your order',
					wc_price( WC()->cart->total ),
					wc_price( $minimum )
				),
				'error'
			);

		}
	}
}
add_action( 'woocommerce_checkout_process', 'wb_wc_minimum_order_amount' );
add_action( 'woocommerce_before_cart', 'wb_wc_minimum_order_amount' );